The kit lens is an 18-55, and its f/stop number only goes as low as 3.5-5.6. The 50mm f/1.4 is a prime lens (non-zoom) and it goes to f/1.4 for a very shallow depth of field and allows much more light into the camera than the kit lens. The sharpness is incredible. Its a $400 lens. Heres a link for more info:
Canon U.S.A. : Consumer & Home Office : EF 50mm f/1.4 USM
Mine is only roughly 4-5 months old and has only been used for shoots 5-6 times. Almost new condition.