PTZ is a system built into some cameras which allows them to:
Track objects moving through a scene by steering the camera using joystick-like controls.
Zoom in and out to see more/less of the surrounding area.
Set preset camera positions that use coordinates to automatically move to that location when selected.
Set a home position where the camera will return after a period of user inactivity.
Set a PTZ tour, where the camera will automatically jump between different camera presets to allow you to monitor different local locations on a rotating basis.
The PTZ capabilities are determined by your individual camera - you may find that there may be differences between different camera manufacturers/models including maximum zoom, full 360 rotation, maximum tilt up and down.