Tram vehicles are usually lighter and shorter than main line and rapid transit trains. Today, most trams use electrical power, usually fed by a pantograph sliding on an overhead line; older systems may use a trolley pole or a bow collector.

In most modern systems, the tram rails themselves are not electrified; they serve as the "return path" for the electrical circuit rather than the primary power source. Most trams draw power from overhead wires via a pantograph or trolley pole. However, there are exceptions: some older systems (like those once found in London or Washington D.C.) used a "conduit" system with a third rail hidden in a slot between the tracks. More recently, "ground-level power supply" (APS) systems, popularized in cities like Bordeaux, use a specialized third rail that only electrifies the segments directly underneath the tram as it passes. While the rails carry a return current, they are typically grounded to ensure they are safe for pedestrians and vehicles to cross without risk of electric shock.