Railway platform - Wikipedia

A railway platform in the broad sense is a strip along the railway track at a train station or tram stop where passengers can board and unboard.

In the most primitive form it is on the same level as the track, and there is a fairly large height difference between this 'platform' and the train floor.
Usually the platform is at an elevated level relative to the track but lower than the train floor.
Ideally the platform is at the same level as the train floor.
Occasionally the platform is at a higher level than the train floor. This may be the case when a train with a low floor level serves a station built for trains with a higher floor level, for example at the Dutch stations of the DB Regionalbahn Westfalen (see Enschede). Likewise, on the London Underground some stations are served by both District Line and Piccadilly Line trains, and the Piccadilly trains have lower floors.

A tram stop in town is often in the middle of the street; usually it has as platform a refuge with a height like that of the sidewalk (ca. 10 cm), sometimes no platform at all. The latter requires extra care for the boarding and unboarding passengers and for the other traffic to avoid accidents.

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.

Fiction: platform 9 3/4 (Hogwarts Express, Harry Potter).