In most cases a par can is simply a light that holds a par lamp in it. In general the can is simply a holder for whtever the lamp is going to produce as far as light output in both shape and intensity. Par cans are most commonly used for color washes whether it be for a back light washes or curtain warmers from the front. They do easily blend together. A par can does not have many accessories. In general they can hold color frames, barndoors, and top hats.