Action Function in Salesforce ?

Action Function is an apex component in visual force page. Apex: Form tag enclosed in the action function tag, which can be able to call the controller method. Action function invoked from the JavaScript as XHR (XML Http Request).   For Details <apex:form > <apex:actionFunction action=”{!register}” name=”registerStudent” rerender=”showstate”> <apex:param name=”studentData” value=”” /> </apex:actionFunction> </apex:form>