PAR CANS
Par 38
These lights look like the common floodlight that you may use to light up the outside of your house, driveways, etc. They have a screw base and inexpensive to purchase and maintain.
For most uses these lamps are installed in what is commonly know as a "can" which limits the light radiating from the side and also provides the ability to mount a sheet of film know as a "gel" to provide a colored lighting effect.
Par 56 & 64
These are the largest lights in the PAR family. They look like automobile headlights and mount in a "can" similar to the Par 38. However, the lamps are mounted by their rim so they are free to rotate in the "can". Par 56 & 64's beams are oval and can be rotated at the socket to deliver either a vertical or horizontal dispersion of light.
Par 56 & 64's are available in 300 & 500-watt incandescent lamps and 500 & 1000 watt quartz. Also, a variety of beam spreads are available from Wide Floods to Narrow Spot (most popular for bands & performers). Please remember using high wattage lamps close to the performers will definitely irritate them.