Subject Tracking
A mode in which the camera identifies a chosen subject and follows it around the frame, moving the active focus area to match.
In depth
Tracking combines focus distance with pattern, colour and depth information, so it can hold a subject that briefly passes behind an obstacle or turns away. It frees the photographer from keeping a point on the subject, which changes how a fast sequence is composed — you can frame the picture rather than aim the autofocus.
Examples in practice
A tracked skier stays in focus while the photographer recomposes to place them in the bottom corner of the frame.