What is an action?
An action is what a visit can do: visit a page, click on a link, wait X seconds, or fill out a form.
For example, if you want a launch to visit two pages and wait 45 seconds between, it will be 3 actions (action 1: visit a page, action 2: wait 45 seconds, action 3: visit another page).
With a plan giving you 3,000 actions each day and if you configure a campaign with 3 actions (visit the first page, wait 40 seconds, and visit a second page), it means you will receive 1,000 visits each day.