Cruiser bikes are like hybrid bikes and designed for comfortable, casual riding. Most cruiser bikes are single- or three-speed and have the old-fashioned coaster brake (you pedal backwards to stop). They can be used for short-distance commuting and errands, as long as your route is fairly flat.
Flat-foot comfort bikes are a sub-category of cruiser bikes. The frame lets you ride with the seat low enough to place your feet flat on the ground when you’re stopped, but you still get full leg extension while pedaling.