When I look at Mastodon posts, I see a decent amount of replies and boosts for popular posts, but not very many stars (see example image). I assumed a star is the same as a like, but I feel not a lot of people star a post, whereas I did see a lot of hearts/likes on Twitter posts. Are they not equivalent?
On Masotdon, likes don't do anything to extend the reach of a post or make it popular in an algorithm like Twitter. It's literally just a regular like/favorite button, so use it if you want to like/favorite a post.
Edit: also yes, federation as others have said.