The <apex:actionRegion> component specifies the components to be processed on Force.com server. If no <apex:actionRegion> is defined the whole View functions as a region:
Please go through the link below, it has sample code which explains the concept better: http://www.tgerm.com/2010/09/visualforce-actionregion-deep-dive.html
<apex:actionRegion> or actionRegion provides an area of a Visualforce page that decides and separates which components should be processed by the force.com server when an AJAX request is generated. Only the components which are inside actionregion component are processed by server, so it increases visualforce page performance.
For more detailed example, check below link: http://www.sfdcpoint.com/salesforce/actionregion-visualforce-salesforce/
@Akshay Deshmukh example is the most valid example of actionRegion. actionRegion is not for purpose of bypassing validations rules as explained in some of the blogs. Salesforce used validation rule for better understading. if you need to bypass validation rules you can always use immediate=true. @Akshay explanation is perfect example for action region
The <apex:actionRegion> component specifies the components to be processed on Force.com server. If no <apex:actionRegion> is defined the whole View functions as a region:
Please go through the link below, it has sample code which explains the concept better:
http://www.tgerm.com/2010/09/visualforce-actionregion-deep-dive.html
For more detailed example, check below link:
http://www.sfdcpoint.com/salesforce/actionregion-visualforce-salesforce/
You can check my blog for more detailed information with example
http://dattarajsfdc.wordpress.com/