A railway platform in the broad sense is a strip along the railway track at a train station, metro station or tram stop where passengers can board and unboard.
Sometimes a tram stop is served by ordinary trams (with rather low floors) as well as metro-like light rail vehicles with higher floors, and the tram stop is provided with a dual height platform (along the track first one height, then an extension with the other height). This applies for example in Amstelveen, Netherlands.
Similarly a train station may be served by heavy-rail and light-rail vehicles (with lower floors) and also have a dual height platform. This applies for example on the RijnGouweLijn, Netherlands.
A railway platform provides access to one or two tracks; if it is fork-shaped on one or both ends the number of tracks will be more. Usually not the platforms, but the tracks are numbered. Tracks without platform access, used for through traffic, also have a number. This number may not be indicated, but it shows indirectly by the fact that in the numbering of the accessible platforms a number is skipped.
Some metro stations have screens with doors between the platforms and the tracks. They provide more safety; also they allow the heating or air conditioning on the station and the ventilation in the tunnel to be separated, thus being more efficient and effective. They have been installed in most stations of MTR, Hong Kong, see picture.
Fiction: platform 9 3/4 (Hogwarts Express, Harry Potter).