Video analysis includes tasks such as analyzing the motion between successive frames in a video, tracking different objects in a video, creating models for video surveillance, and so on. OpenCV provides a module called video that can handle all of this.
There is also a module called videostab that deals with video stabilization. Video stabilization is important, as when you are capturing videos by holding the camera in your hands, there's usually a lot of shake that needs correcting. All modern devices use video stabilization to process the video before it's presented to the end user.