New sync for Lemmy user here. What's different for a community that I subscribe to, than any other community? I mean .. For me to subscribe in the first place, they mostly have to show in my feed to begin with.
Subscribe lets you build a custom feed of communities that youre specifically interested in. Use it as a filter to see the topics you care about.
As an example, I'm subscribed to "sync for lemmy" and saw your question. If I was just in "local" or "everything" its fully possible that i would never have seen any sync for lemmy content at all.