This is a simplified explanation of what Behavior Analysts call Functional Communication. However, no matter what you call it, it is an import part of decreasing challenging behavior; as telling a learner to stop, or expecting them to simply disengage in the challenging behavior, won't likely get you the results you want.
This youtube video is a fun five minute visual of the four functions of behavior (e.g., attention, access, avoidance, and sensory).
Click the video to see more!
This is a ten minute video explaining what functional communication is, different forms communication can take on (i.e., PECS, Dedicated Devices, ALS, etc) , and how to reinforce functional communication.
This youtube video shows how to teach students to escape a situation appropriately (i.e., without aggressive or disruptive behavior).
This is a link to a practical guide for how to go about teaching functional communication, and research supporting it to help decrease challenging behavior.