In Struts 2, sometimes you may want to process another action when one action completes. For example on successfully submitting a form you want to render output from other action.
This can be done by two methods
1) Action Chaining
2) Action redirect
** UPDATE: Struts 2 Complete tutorial now available here.
Difference between Action redirect & Action Chaining:
Difference between Action Chaining & Action redirect is, Action Redirect starts from scratch, it is like you called the other action class for the first time while Action Chaining keeps the values of the first Action class on the value stack and adds the variables of the new action. Look at the example below to understand the above concepts.