What is ActionStatus ?

ActionStatus visualforce component displays the status of an AJAX update request. An AJAX request can either be in progress or complete. It can be done using apex:actionStatus

Depending upon the AJAX request status (whether AJAX request is in progress or complete), this component will display a different message to the user. In many scenarios, the AJAX request takes some time. So we should display some message to the user that your request is in progress. Once request is complete, we can display some different message to the user.

Using actionstatus, we can also display some gif (Graphics Interchange Format), which shows to the user that their request is in progress. It gives a very good presentation to end-user.