Think of a shotgun choke like the nozzle on the end of a garden hose. Tighten the nozzle, and you get a narrow stream of water that reaches out some distance. Loosen it, and the stream widens and doesn’t go nearly as far. Same with a shotgun choke. A choke constricts (tightens) the shot charge immediately prior to the charge leaving the muzzle. A tight choke, like a full choke, helps hold the pattern together farther away; a less tight choke, like improved or modified, allows the pattern to widen or spread for shooting at moderate distances.