Reading something like the Wikipedia entries for both should give you more than enough information to differentiate the two.
Spring uses AOP for its transaction management. Struts doesn't use it at all, unless the developer uses it to do something--you can use AOP *with* Struts, but it provides no mechanism for doing so. Implementing AOP is *completely* outside of the problem Struts tries to solve.
Consider, however, a web request filter (a servlet
spec filter, a Struts 2 interceptor, etc.). The developer has access to the request--so filters (or interceptors) are "around" advices for a web request. It's (limited) AOP in nature, applied to a higher-level construct than a method.