Even though it was made with gaming in mind, it's easier to think of it as... well like @ZatchZ said: kind of like skype, but not xD Or like any messenger if you're familiar with them (ala facebook messenger, Instagram PMs/Group chats, etc.)
Anyone with an account is free to create their own "Server" which is just a collection of different chat rooms (either text or voice based ones) and then you can send people weblinks to invite them to the server. Or post them publicly for people to find and join, or whatever- depending on how private the server owner wants their server to be.
Like for example on my list of servers, I own like 2 or 3 (1 for a Competitive Pokemon Draft League I run, one for like 5 of my friends for Splatoon, and one for a Guild in an MMO I used to play) and I'm a member of several other ones: Various art/comic related servers, another pokemon draft league, ones that comic collabs that I've joined have used to organize said collabs, etc.