Welcome to the fediverse. I am sure people can explain this better, if you consider the likes of facebook, twitter and I guess reddit being centralised, there is one controller, that one controller calls the shots as to what happens.
With fedi, there are multiple services, hosted on instances, each instance is owned by individuals, all these services can talk to each other. Similar to how you get e-mail hosted by different people but you can communicate with anyone using e-mail regardless of service owner.
I think what we want to build here, goes back to the 1990s at least in terms of people were hosting sites themselves, there were no BIG corporations dictating things or monopolising the internet, lots of search engines for example, plus different services web, e-mail, usenet (nntp), gopher etc. So in a way back then it was kinda disjointed but people were in control more. If I understand the reddit situation, people were on there, using 3rd party apps to connect, then it was decided to change how things worked, and people were locked out, just a top down decision which has backfired in terms of people just leaving.
So yeah, back then it was fun, I remember having small irc (internet relay chat) servers, for my local lug, and different members also had them so we all connected to gether, so it did mean 1 server 1 user for them but they were learning how to run irc services, but you could do that back then, hang a web server from your internet connection, or more so if you had something like isdn (128k) rather than the fastest dialup (56k). Service providers were more hacker friendly in thast respect.
So on fedi we can kinda of get some of that back, collaborate and do what we want (within reason) in terms of running little or perhaps larger services.