The tractor beam was a useful bit of technology that the Galactic Empire acquired by capturing and torturing James T. Kirk and Jean-Luc Picard in an agonizer booth... which they acquired by capturing and torturing the mirror-universe Spock. Palpatine hated Star Trek. Besides, Kirk and Picard both stole it from E.E. "Doc" Smith anyway.
The beam was a projected force field that could move or immobilize matter at a distance. It was usually used to move starships around in space, to guide them safely into landing bays, and then to board them and kill everyone.
The Millennium Falcon was once captured in a tractor beam and brought inside the Death Star, but Han Solo could have avoided it by modifying his deflector array to emit a polarized antigraviton beam, but he hated Star Trek more than Palpatine, so he didn't know how to do that.
Tractor beams could not be used in agriculture or moisture farming. Don't be a moron.