View > Camera Tools
> Track Tool
Tracks
the camera vertically and horizontally. You can also press 
+ 
. Hold 
to constrain
the camera movement.
View > Camera Tools
> Track Tool > 
If off, as the camera moves an object moves at a speed that may be different than the speed of the cursor. This problem occurs with objects far from the camera. Track Geometry is off by default.
If on, as the camera moves, an object moves at the same speed as the cursor. The object selected at the beginning of the Track operation remains under the cursor.Tracking is slower (especially if there are many objects in the scene) if Track Geometry is on.