Tram (British English, tramway; also known as streetcar in American English) is a rail vehicle for use in urban areas. Trams are almost exclusively used for public transport, though there are also few cargo trams; for example, current cargo tram operations are executed in Dresden and Zürich.
Trams run on electricity from overhead wires. There are few exceptions, such as trams in Bordeaux with a ground-level power supply.
The main difference between a 'tram' and a 'metro' is that tram lines can run in the streets, so a tram moves with other traffic, while a metro is always separated from all other traffic. There are still some systems in-between tram and metro, for example in Volgograd, Russia, where tram vehicles use segregated infrastructure.
The other similar system is light rail. There is no well-defined difference between the two, but light rail is generally faster, uses longer trains and has more segregated infrastructure.