A component that provides support for invoking controller action methods directly from JavaScript code using an AJAX request. An <apex:actionFunction> component must be a child of an <apex:form> component.

A component that provides support for invoking controller action methods directly from JavaScript code using an AJAX request. An component must be a child of an component.

Unlike , which only provides support for invoking controller action methods from other Visualforce components, defines a new JavaScript function which can then be called from within a block of JavaScript code.

Note: Beginning with API version 23 you can't place inside an iteration component — , , and so on. Put the after the iteration component, and inside the iteration put a normal JavaScript function that calls it.