a4j:status is an indicator of an Ajax request. It has two states - start and stop. The start state indicates that an Ajax request is in progress. When Ajax Response comes back, the component switches to the stop stage.

Status could be defined:

- Default for View
- Default for form
- Referenced explicity from the component which sends request

Example of View scoped status. It should be defined outside of any form and will handle all the Ajax requests within the view.