RSS feed is a link that certain programs (or you manually) can pull new posts of a given place from, and the fediverse is full of those. Usually people use those to get posts in an unified and local feed, but helps as a way to list those you'd follow if they become unreachable, and being (usually) locally managed, no one can legitimately reach to your machine to shadowban them or the sort.

Give me a few minutes and I'll record a video exemplifying.