How do you navigate discord?

I see every other reddit community has discord servers and I feel like I am missing out by not being part of them. At the same time I am still trying to understand the purpose of these discord servers.

Anyways I joined a few of them from the links in the wiki, like 'The Green Discord'. But I am not able to navigate them.

There is just so much (not so structured?) activity, I can't figure out where to start and what to use it for. And I am finding it difficult to follow threads of discussions, maybe due to the UI, idk. I had to also turn off the notifications right away because they just kept coming like bullets.

Please help me with some guidance.

P.S.: I have experienced similar difficulty navigating slack at work.