Breakoff is the planned altitude at which jumpers in a group stop what they are doing, turn away from each other and track off to create horizontal separation before deploying.
Separation before deployment
Canopies open across a substantial area, so jumpers who deploy close together risk collisions or entanglements. Breakoff creates the space that prevents this.
The altitude is agreed in the briefing and rises with group size — a larger group needs to start separating higher because more people need more room.
Tracking
Tracking is the body position used to travel horizontally in freefall: legs extended, arms swept back, body angled to convert some vertical speed into forward movement. It is the mechanism by which breakoff actually creates distance.
These pages explain what things are so the language makes sense. They are not instruction and cannot substitute for it — skydiving is taught in person by rated instructors at a drop zone, and anything involving equipment handling or emergency procedures belongs there rather than on a web page.