The real problem with social networks like Facebook and Twitter is that they require using their servers that store all of what you write and share. By nature of the fact that you are using their servers Facebook and Twitter have the right and ability to access what you write and share.
A peer to peer network takes a server, like Facebook and Twitter’s, out of the middle. What you write and share goes directly from your computer to the computer of others on the peer to peer network. Because this information can actually end up on many more computers most peer to peer networks encrypt what is passed around. Consequently, only the people who have access to your public or private keys can actually read what you write. (By the way, in a simple way I have just explained one reason why blockchain has been written so much about.)