The choking of a shotgun can be extremely important depending on what you are hunting.
In a 12 gauge, the choking is the difference from the bore diameter to tightest part of the choke. A cylinder bore has no diameter change, and would be an extremely poor choice for turkey hunting.
The standard constriction of the chokes for a bore barrel of .735 would be as follows:
Cylinder = 0.000
Skeet = 0.005
Improved cylinder = 0.010
Light modified (or skeet-2) = 0.015
Modified = 0.020
Improved modified = 0.025
Light full = 0.030
Full = 0.35
Extra full = 0.045
Super Full 0.055 (or tighter)
Most turkey chokes are extra full or tighter. I typically use a full choke which is good out to about 40 yards (an extra full would give me an extra few yards, but make the closer shots a tad more challenging).
You are trying to get a lot of small pellets into a small area to hit the neck or skull, and the thin patterns of a cylinder choke would make shooting a turkey unethical out to most reasonable distances.