Each of those projects are installed onto different computers (called nodes), and those nodes talk to the others, and together make the full Federation. Any post you make can be viewed from any node.
Unlike other networks like Facebook, you see what you want, not what they want you to see. Content does not get bumped up because of popularity or what you do on the social network. You follow #hashtags and people to get content in your stream.
If you want to find content here remember to follow #hashtags, and follow other people (by adding them to your contacts). The same thing applies the other way as well. No one will see your posts unless you tag them
It is our job as the community to make content, invite people, fight spam, and even work on the projects themselves.