What is the difference between actionFunction, actionSupport, actionRegion in Salesforce?

Hi Prachi,

<apex:actionFunction>
This component provides support for invoking controller action methods directly from JavaScript code using an AJAX request and we can use action function from different places on visual force page.

<apex:actionSupport>
<apex:actionSupport/> Invoke the controller method using AJAX when event occurs on page like onMouseOver, onClick, etc. and we can use action support for particular single apex component.

<apex:actionRegion>
An area of a Visualforce page that demarcates which components should be processed by the Force.com server when an AJAX request is made. Only the components in the body of the <apex:actionRegion> are processed by the server, thereby increasing the performance of the page