San Francisco's historic cable cars are popular but misunderstood.
They are not trolleys. Trolleys are powered by electric lines overhead. Cable cars are powered by a system of cables that move constantly in channels beneath the street. The gripman operates a clutch that grips the cable, causing the car to move, and releases the cable to stop the car.
They aren't used for transportation any more. There used to be fourteen lines fanning out over the eastern portion of the city. They were invented because there were accidents involving teams of horses pulling heavy loads up the steep hills in the city.
Now there are just two lines. The Powell Street car runs from Market Street, up and over Nob Hill and winds up a Fisherman's Wharf. At either end you can watch a turntable turn the car around to go the other way. It is hugely popular with tourists
The California Street car (pictured above) starts near the Embarcadero, runs up and over Nob Hill and ends at Van Ness Avenue. The latter half of the ride is mostly residential and there's no tourist destination. Usually there's no waiting in line for this one. Just hop on!
I suppose every now and then someone rides them just to get from here to there, but mostly they are museum pieces, and delightful ones at that, although they are expensive.