What is an In-page action? Please help me!

I was wondering if you could help me out.

I am having difficulties with in- page actions. What is an in-page action? Is it a session? A sequence of page views? Not needing to load a new url? A collection of session by one user?

What are some examples of in action? Is it goal conversion? Page view? Video starting?

Also is it the same as Call to action?