On Lemmy, both upvotes and downvotes are aggregated together to give a post a sort of "score". Currently, your post has 1 upvote, which would be yourself. If I were to upvote your post, this number would become 2. If 2 people were to downvote your post, however, it would become a -1. This does make it harder to judge the full reaction to a post, but some clients add a percentage next to this score to show the overall amount of people who upvoted vs downvoted. Also note that some Lemmy forks (like Mastodon or KBin) are also a microblogging platform that may not take upvotes/downvotes into as much consideration as opposed to other options.

As for sorting, that is highly instance/client dependant as different instances can use different filters and algorithms to show you the same labelled sort category.

Keep in mind that Lemmy was never supposed to be a reddit "replacement" and is its own platform entirely, some features do not have direct translations in that way. I would also like to say I moved to Lemmy during the initial reddit migration and learned from many meta posts explaining these topics then, if someone has better/more detailed information feel free to correct me.