Draft control operates by sensing the amount of "pull" on a ground engaging implement. If while using such an implement the tractor happens to get stuck, the draft control will lift the implement over the obstruction.
This is mainly used for plowing operations, but is also sometimes useful when using a boxblade or scraper blade. When using draft control a constant ground speed should be maintained.
My owners manual advises to not enable this feature when using non-ground engaging implements, and unexpected movement of the lift arms could result.
Check your owners manual for details about how this feature is implemented on your tractor.