what is the meaning <a4j:ajax event

[mk_roger]

this event attribute is custom or not?,   if not ,please tell me  what  event attribute could be attach this tag.

[snjv180]

<a4j:ajax is used to send a ajax request event attribute is used to trriger the ajax request on a selected event.

<a4j:commandButton id="btn">

<a4j:ajax event="click" render ="@form">

</a4j:commandButton>

This will check for click event and reRender the form when the button is clicked via ajax. (i.e ajax request is sent to update the form)

[mk_roger]

thanks