As someone who's still new to agile, I'm not sure I completely understand the relationship or difference between user story, feature, and epic.

According to this [question](https://stackoverflow.com/questions/1707820/what-is-the-difference-between-a-user-story-and-a-feature-in-agile-terminology), a feature is a collection of stories. One of the answers suggests that a feature is actually an epic. So are features and epics considered the same thing, that is basically a collection of related user stories?

Our project manager insists that there's a hierarchical structure:

Epic -> Features -> User stories

And that basically all user stories must fall within this structure. Therefore all user stories must fall under an umbrella feature and all features must fall under an epic.

To me, that sounds awkward. Can someone please clarify how user stories, features, and epics are related? Or is there an article that clearly outlines the differences?