Video annotation focuses on labeling objects, actions, or events in video frames to train AI models for applications like object tracking, action recognition, and autonomous driving. It involves frame-by-frame annotation to ensure precision, object tracking to follow the movement of labeled items across frames, and event annotation to identify specific activities (e.g., a soccer goal). Additional techniques include scene annotation to label the environment and context, and keyframe annotation to reduce redundancy by annotating only critical frames.