The technical description of a projector lamp is that it is an ultra-high pressure mercury vapor ARC lamp. Projector lamps are scientifically categorized as metal halide lamps and Philips has protected the name "UHP lamp" for its projector lamps.
Projector lamp works by sending an electric current over an ARC distance, the ultra-high pressure mercury vapor. The electricity illuminates the mercury vapour, which causes the lamp to emit a light of extreme intensity or brightness. The bright light caused by this process radiates onto an LCD (liquid crystal display) or DLP panel, creating the fantastic images for which the projectors are known.
Projector lamps have a complicated technology that are very expensive for the producer, for which reason they tend to be expensive.