MT's system is complicated and painful. There are some errors in people's explanations as well.
MT has General Tags and Limited Entry Tags
General tags are OTC for residents. Total NR tags are capped by a quota. Most of the state can be hunted on a general tag.
75% of NR general tags go to those with the most Preference Points, 25% given randomly. You are only allowed to buy Preference Points for two years without actually applying, after that they expire. You are able to buy a preference point with your application that counts towards that application so if you buy 1 now and 1 with your application next year you go into the draw with 2 preference points.
Bonus points just put your name in the hat more times if you are applying for limited entry tags. If you are only looking to hunt in a general unit, there is no benefit to purchasing bonus points.
Also, in order to be in consideration for a limited entry tag drawing, you must first draw a general tag. This is nice if you are happy to hunt on a general tag if you fail to draw your limited entry tag or crappy if you only want to hunt on a limited entry tag because they take a nice chunk of change (roughly $300 going off memory) if you return your general tag upon failing to draw a limited entry tag.