Many of the instances are organized around a particular community. For example, toot.cat is for "cats and the people that love them". witches.town is "made to p

Many of the instances are organized around a particular community. For example, toot.cat is for "cats and the people that love them". witches.town is "made to provide a nice place on Mastodon for queer, feminists, anarchists and stuff as well as their sympathizers." However, as you'd expect, you might not talk strictly about cats on toot.cat, but you'd be talking with other cat lovers. It might be difficult to discern the community from the local timelines. Also, some of the ones that you mention are just general social instances. Each instance has an about page that you can look at to get a better idea of what it is organized around. [1] [1]: https://mastodon.art/about https://mastodon.art/about