@oncehandsome
Discord is a chatprogram, yes. You can use it to chat and (video) call with other people individually, or you can join servers hosted by specific communities. I use it to videocall with IRL friends, as well as with people from my FAF clan when we play together. FAF itself has a dedicated server where a lot of people that play FAF hang out, and it also serves as a general information hub.
Don't worry about minimizing apps running in the background. Unless your PC is more than 15 years old or really, really, shitty, you will not notice the difference. For reference, my PC is coming up on its 10 year anniversary, and while I am certainly starting to notice it being not up to par for some of the mapping work that I do, discord has never been an issue.
Alternatively, you can close the program when you're done chatting or looking through the mapping documentation, of course. No system drain if you don't keep the software running.