Welcome to WordPress. This is your first post. Edit or delete it, then start writing!
These actions are run when a logged-in user opens the Posts page in Version 3.3.1. This list shows only the first time an action is called, and in many cases no function is hooked to the action. Each admin page has a different list of actions depending upon the purpose of the page and the plugins installed. This list should be viewed as a guide line or approximation, and not a concrete specification.
In these actions, (hookname) depends on the page. For the Posts page it is edit.php, or for a theme’s Background page it is appearance_page_custom-background.