Basically, choke is the measure of the muzzle inner diameter. Essentially, the smaller the diameter, the tighter pattern it will shoot. You barrel should have a single letter stamped in plain sight. F = full choke or good for long shots. M = modified or a larger pellet pattern. THis is an over-simplification, but if you do an engine search for shotgun chokes, you will get a much better explanation.
The different loads I mentioned have different power levels. If you are hunting turkey, it's to the hunter's advantage to have more power as those birds can be difficult to kill. Doves & clay pigeons are much easier & require less power. At the sporting goods outlet, ask a sales person for the light loads like dove or trap & you will be in biz! SW
I am really not an expert - distinguished or otherwise!!