How to include bumped posts in RSS feeds?

What does it mean to “bump” a post? Is it when there was an answer?

Currently, my RSS reader gives me a notification when there is a new post, but not when someone answered to a post. I am not sure if RSS has a notion of “answers”, and I am wondering if I understand correctly that this “bump” info would let my reader know that the post was updated and it would (maybe) trigger a notification?

Currently it just feels a bit useless to use the RSS feed, given that anyway I need to open the website to see if there was an answer posted in the topic I am interested in.