Melissa Coates offers up an explanation:
If you hear the question: “What’s a Power BI app?” you might think there’s a straightforward answer. However, the term ‘app’ is pretty overloaded term in the world of Power BI.
One time I was presenting a session and talking about Power BI apps vs. workspaces – right in the middle, someone in the audience starts asking me a Power Apps question because they thought I was talking about that (which is a VERY different thing). That was a big reminder to not to assume that we all have the same understanding of terms.
Read on to learn what a Power BI app is, as well as why it’s a rather useful concept.