ELI5: In computer networking, what is a port?

So, you know when you want to send a letter to someone, you need to write their address on the envelope? That address tells the post office exactly where your letter needs to go. But imagine if the person receiving the letter lives in a big house with many apartments and many people. Just the house address might not be enough. You might also need to specify the apartment where the person you want to receive the letter is located.

In computer networking, the 'address' is like the IP address of a computer. It tells the network where to send the information. But computers are like a big house converted to apartments. They can do many things and run many applications at the same time. Each of these applications is like a person in a different apartment in the house.

The 'port' is like the apartment number in the house. When information arrives for a particular IP address (the house), the port number (the apartment number) makes sure the information gets delivered to the right application (the right person in the right apartment).

So, when you play an online game, or use a web browser, or send an email, each of these applications uses a different port number. This allows your computer to know which application should receive the information that's coming from the internet.

In summary, in computer networking, a port helps your computer sort incoming and outgoing data so it goes to the right program.