AOP works by separating common concerns across the layers in separate classes and names them Aspect. Aspects have APIs which aim to solve a common problem, like logging, and exception handling. These are then invoked while intercepting the actual method invocation. Such APIs are termed Advice. Advices are interceptors, which intercept original method invocation and wrap it around with handling of cross cutting concerns.
Now, for applying Advices to methods, AOP provides artifacts named JoinPoint. Using a JoinPoint we could define, which API invocation would be wrapped around by what Advice.
Note
AOP alliance http://aopalliance.sourceforge.net is the driving force behind standardization of various AOP implementations. AOP alliance seeks to separate the implementation part from the weaving part. Here, it provides a set of interfaces, which represent the MethodInterception, Advice, and JoinPoint. Guice provides its own implementation for the same.