The difference between light rail and streetcars, in today's typical transit systems, is that light rail tends to be a regionalish system with stops less frequently (maybe 12 blocks or so) except in downtown, while streetcars are a local transit system that operates a lot like a bus. Portland, Oregon has light rail (MAX) and is building a streetcar. The light rail line runs some 33 miles from the suburbs to downtown, while the streetcar runs about 3.5 miles from an inner neighborhood to downtown, with stops every 2-3 blocks or so.