Decentralized social networks and communities provide a higher level of control and autonomy for members than centralized ones. There are also federated decentralized social networks and communities. The principle of interaction between users is significantly different.
For example, Twitter allows users to post and receive messages only to those with Twitter accounts (for example, Twitter users cannot post to Facebook accounts due to the lack of cross-platform). Federated decentralized social networks and communities allow users to communicate independently of the network and community. This is the main difference between decentralized social networks and centralized social networks like Facebook and Twitter.