How do browser extensions learn about user activity/inactivity?

Question

Browser extensions

How do browser extensions learn about user activity/inactivity? By what signs - mouse movements, opening pages, clicks? The task, as you understand, is to simulate activity.

Answer 1

The extension can do just about anything. Track browser opening/closing and almost any activity inside the browser.

Answer 2

The answer is found empirically - the opening of the pages. The question is closed.