It’s hard to tell without some more context, but in a general sense, I would assume an in-page action to be any action the user can perform on a given page, without navigating to a new page.
Sometimes this is clear cut, but it’s less clear when dealing with interactions such as launching a modal window or similar actions on a complex SPA.
Exactly what could constitute an in-page action would depend on the specific page and exactly what your particular criteria are. Examples might include:
- Clicking on a button
- Entering data into a form
- Hovering over something without interacting
- Playing a video, stopping a video, rewinding a video (examples here to indicate that the level of granularity is dependent on use case)
There isn’t really a canonical answer for what an in-page action is, they are often defined by your business and what it needs/wants to track in terms of actions.