ELI5: The rules of D&D

Why not read the basic rules?

https://dnd.wizards.com/what-is-dnd/basic-rules

https://www.dndbeyond.com/sources/basic-rules

The simplest explanation: roll to hit, then roll for damage. Or roll a save if it doesn't need to hit. Or roll a skill check if you're trying to attempt something out of combat.

That's about it. You can find the details in the rulebooks.

Players say what they want to do. DM tells them to roll dice. DM tells them what happens depending on the dice roll.

Player says what they want to do.

DM decides how difficult it is from trivial to impossible. If it's possible and not trivial the DM sets a difficulty and tells the player what ability and/or skill Bonus to use.

Trivial tasks always succeed, impossible tasks always fail.

Player makes the roll and calculates the outcome.

DM determines the outcome and tells players what happens.

That's the base of dnd. The other rules are all just for determining or changing difficulties, as well as changing what's possible, and what's trivial. And to create an order of operations.

Basically, you need a Dungeon Master who will be the story teller. This person is responsible for setting the stage for the story and guiding the adventurers through their quest. The DM also sets up the encounters with monsters. The DM must know each monster, the Hit Points, the Attack Power, special moves, etc for each monster.

The adventures will listen to the opening sequence of the story by the DM and then they will make decisions on what to do next. The DM will guide the players to what they "should" do, but the DM doesn't "force" them to do anything.

The DM must be able to think on their toes, for players will always try to do something the DM didn't think of...they must be able to quickly act on a situation. Speaking of quickly act, the DM can take their time to figure out what to say next, just don't take like 10-15 minutes, or everyone will get bored.

For the players, try to stick to the story as much as you can, don't go running off and trying to fuck chickens (yes I had a player who wanted to do that all the time).

The players must keep track of their health, inventory and skills. They must know how and when to use certain skills.

I could go on and on, but I see others are commenting now and probably discouraging based on your question, so I will keep this short and hope this is what you are looking for.

Oh, and HAVE FUN, that is the most important part!

The basic rules are available for free on the WOTC website: https://media.wizards.com/2018/dnd/downloads/DnD_BasicRules_2018.pdf

In general I'm increasingly of the opinion that rules-lite is the way to go. Check out Shadowdark for an even more streamlined version of 5e that, imo, cuts out a lot of the cruft. Each class's rules take only one page. Same with character generation.

There's no avoiding it. You're going to have to read the books. A good game of D&D is 90% improv, so it's mostly about crafting a story together. But the rules of the game (as interpreted by the DM) make the world consistent and makes it feel more "real".

As far as the rules go, there's a few basic steps that are pretty consistent regardless of whether your fighting, or using a skill, or interacting with the environment.

1. The DM determines a numerical difficulty for the action. So a DC for a skill check or AC for an attack. 10 is easy in either case. 20 is kinda hard.

2. Roll a twenty sided die (called a d20) and add a bonus. The bonus is calculated from an attribute (a base property of the character), your proficiency (which increases with experience), and maybe a bonus from some item line a magic weapon or gloves that make you e.g. good at picking pockets.

3. If your very likely to succeed the DM might give you "advantage" which means roll twice and take the highest number. Likewise disadvantage means roll twice and take the lowest.

4. Regardless of the outcome of the roll, this is the time where you accuse the dice of cheating. It's their job to serve you and they just failed so hurl them across the living room. Now take a good 5 to 10 minutes digging through your bucket of dice to find one that works. Also that roll landed crooked so it doesn't count.

5. Now it's important to remember that the DM is cheating too. No matter what you're doing, your character should absolutely have had advantage on that last roll. You're going to want to lean heavily into your character's back story, because the DM has no control over it. Trying to climb a mountain in a thunderstorm? Well your grandmother was actually a gecko lady. Trying to shoplift a priceless artifact under the eyes of a magical security team? Oh yeah, your other grandmother was made permanently invisible by a sorcerer's curse so now you're periodically invisible too. If you neglected to write a backstory, this is the perfect time to start.

6. Your probably noticing at this point that your table mates are enjoying the game. You have to stop that. If they're having fun then they're winning and you're not. This is easily correctable by pressuring then into role-playing scenarios that no reasonable person would be comfortable with. Access the most unpalatable, "delete my browser history when I die" side of your personality and then force everyone to stew in it like a fart in an elevator while you yiff like there's no tomorrow.

7. It is very important now to change your schedule radically . Attend regularly at first just to get everyone interested in the story. Then decide you need to be in Latvia every Saturday afternoon so now everyone needs to shift their work schedule to suit you.

8. If you've been following along carefully, you're ready to blow up at the DM. This step is great because it's a chance to vent frustration you've always felt with your father for having emotionally and professionally neutered you by constantly withholding affection. Every blow-up is going to be unique but some classics that you'll want to work in are identifying one or more characters as "shameless self inserts", declaring that the game is too hard, and deciding that the setting you helped choose is now boring.

9. Storm out never to return.

Seriously though, have fun. I know this was mostly player-focused. I'll follow up with a summary for DMs when I can.

The basics of all role playing games are the same. A player wants to accomplish something in the game and there will be a resolution mechanic in the game system to determine the outcome. For D&D it's usually roll a d20 die, as some modifier, and try to beat some difficulty number.

D&D 5E has a lot of rules and it can lead you to asking for a roll or looking up a rule for everything. Just remember, rolling is for when the outcome of an action is uncertain or has some consequences, and it's better to just make something up to get past the question you have in the moment and look up the rule later.

It might be easier for you to start with a simpler system with lighter rules. Something like Carin, which has the added benefit of being free!

Good luck, have fun, and don't sweat about getting everything correct the first time!

Besides reading the Basic Rules, which someone else has already linked, I suggest you check out a game on Youtube. Note that usually these aren't an accurate representation of how most games actually go- Critical Role for instance is comprised entirely of experienced voice actors- but it'll give you an impression of how the game runs.

Just don't base your expectations of your players/dm on them.

One important aspect of D&D "rules" is that theoretically there's no specific limit on what your character can attempt. If you say your character attempts something the DM thinks clearly impossible or trivially easy, they may not even have you roll for it. "You plant your hands firmly at the base of the mountan and push and grunt, but you fail to move it noticeably." "You squash the cockroach easily under your boot."

It is a role playing game, and in all role playing games you create a character that resides in a made up world, and use information about that character (these are your character statistics, or your "stats") to attempt to do stuff. The game decides whether those succeed or fail based on your stats and something else. Usually, you play with a referee, or with a computer acting as a referee that has the final say on what happens in the game. The goal is to try to do things

To try to explain the more DND specific (and famous) rules:

In DnD you have 6 base stats: Strength, Dexterity, Constitution, Intelligence, Wisdom, and Charisma. Each character in the game get's a number from 1-20 in each, higher being better. There are other stats your character gets, but these are the core that you use to determine whether you can do stuff in the game.

When you want to perform an action in DnD, you usually have to roll dice to see if it succeeds or fails. Many actions require you to roll a 20 sided die, especially when you want to attack an enemy (a large part of DnD is about simulating medieval/high fantasy combat). Determining whether something suceeds or fails is dependent on your situation and the stats of the characters involved. But rolling a 20 is considered a critical roll, and should always succeed no matter what. Meanwhile, a 1 is a critical failure, and should always fail no matter what.

Another thing that DnD is well known for is the alignment system. Alignment is supposed to represent a characters intentions. A character's alignment depends on two axis: whether they believe in following order (Lawful to Chaotic) and whether they believe in altruism (Good to Evil). You can also be neutral in both, one or neither. Your backstory for why a character has chosen to be this way, or what they believe they are can be made up, but the alignment system generally ties into some of the lore of various DnD settings and affects how other mechanics work, such as certain spells.

Anyway, you can probably tell that there are way more rules than the ones I talked about, but I think those three make up a good chunk of what are the "signature" DnD rules, and what it is well known for.