On newer tractors.. sometimes draft sensigy is achieved by hud components and electronic sensors.. to me.. that's no fun to write about. In the old days.. draft sensing was accomplished by lots of interconnected linkages and valving. Take for instance.. the old ford N series tractors.. the ford 9n/2n/8n ( and many more ) all had draft sensing hyd 3pt lifts.
Head down to a tractor supply and take a look at a tractor repair manual.. specifically a I&T FO-4 manual.. check out the section on repair and adjustment of the hyds.. that shows a part breakdown of the draft sensing valving.. and how the feedback controlls the tractors 3pt lift mechanism.. etc.
Ask questions if you need help.
Another option might be to head down to your favorite tractor dealer, and ask to speak tot he shop foreman. if you are lucky.. you might get a 10 cent tour by the head mechanic, and possibly a quickie draft explanation.
Soundguy