A lot of the "tactical" shotguns with short barrels...have no choke to their barrels ...they're just an open "Cyclinder".
Prior to the 1980's ....all shotguns had barrels with choke restrictions that were fixed, or not changeable. So when I was a kid in the 50's --- we might have had a "waterfowl" gun with a Full choke. We had a "pheasant gun" with a Modified choke....etc..../ because killing a pheasant at 30 yds with a Full choke would destroy the bird vs just kill it ......and trying to shoot waterfowl with a modified choke, would just wound a lot of birds vs kill them effectively ( in general ...there are exceptions ) ...but the point is, we had several shotguns, with different fixed chokes in their respective barrels - for whatever we hunted.
In the 1980's when Browning and others developed barrels that were threaded inside the ends of the barrel ...we had the first screw in, changeable chokes. We could then buy these "choke tubes" ....one for "Cyclinder", one for "Modified, one for "Full", etc....and then use one shotgun, with 3 different steel "choke tube" inserts that threaded inside the barrels...to change the choke in the barrel...and make it a "Skeet gun", or a "Quail gun", or a "pheasant gun", or a waterfowl gun.
So today, when we talk about shotguns....we get into all kinds of stuff on barrel length, etc....on swing characteristics ...and what kinds of changeable "choke tubes" we want to have to make that gun more versatile.
All of this makes it really easy ....along with the wide variety of shells available commercially - especially in a 12ga - with a combination of different chokes and different loads....we can make that 12ga easily perform like a 16ga, or 20ga or even a 28ga....just by changing the choke and the shell we choose. Where 50 yrs ago ...we had 6 or 7 different shotguns...each with a more or less specific purpose / and there was no where near the variety of shells available commercially - that there is today.