There are a multitude of types of planters and drills and price to correlate with what they can do.
Coventional till drill- generally the least expensive, Soil needs to be tilled and prepped prior to planting. Generally have a single disc opener either a grain box with a fertilizer hopper and/or small seed box (legume box)
Min-till drill - This drills have double disc openers that cut the soil and followed by a packing wheel. These drills can be used for no-till purposes in bean stubble and certain cover crops. The double disc cuts a slit in the soil and the press wheel gets the needed seed to soil contact.
No-till drill- Heavy grain drills able to plant seed in soil with zero tilling/soil preparation. The GP606NT posted above is a no-till. They are the cream of the crop and price reflects it. They have trash/row cleaners to clean debris in front of the double disc opener and have much more down pressure to cut into the soil. The seed slit is than closed with a press wheel.
All the drills have a similarity where they are all spaced about 7-8 inches and have dedicated seed boxes. The grain box can run large seeds like rye, oats, buckwheat, and wheat. The legume box is much smaller and is for smaller seeds such as clover, brassicas, rape, clover or alfalfa.
Planters are for row crops such sunflowers, corn, beans, or milo. They are generally set up for 28-30 row spacing. These usually come with fertilizer hopper for side dressing the seed with a low N fert such as 6-24-24. The main benefit of these is they meter much more precisely than a drill and are less like to crush larger seeds which grain drills will sometimes do. These planters also come in conventional till and no-till models.
Do some research on what may work best for you and what you are trying to establish. I have an old JD 290 corn planter and an old JD/Van Brunt 13 row grain drill with a legume box that I use both exclusively for food plotting. I got both items off craigslist for less than 700 dollars total. Both implements are small enough for my uses and didn't break the bank. On a side note though for my plots of a 1/2 ac or less or really shallow plantings such as brassicas my broadcast spreader gets put to work.