In some countries trains are designated by “platform”. But, as you can see, in Chicago several different trains can leave from the same “platform” and directions to trains are given by “track” number. In this short video (0:32), you can hear an announcement of an arriving train that says in part, ” “arriving track number one please stay behind the yellow line ’til the train comes to a complete stop… Indiana, the South Shore… now arriving track four…”
In the underground “pedway” that has been gradually expanding under the city, directions are marked to various “tracks”:
At Millenneum Station, Tracks 8 and 9 are accessible from the same platform. The area between tracks 9 and 10 (Sign: “This Platform Closed”) is referred to as a “platform” even though it isn’t elevated. Tracks 10 and 11 are also accessed from the same platform; here a train is waiting on Track 11.
At the Van Buren Street Station, again two tracks are accessible from the same platform. The first picture is Platform 2 taken from Platform 1, with Tracks 1 and 2 in between. The second photo looks towards the Loop. From left to right, Platform 1, Track 1, Track 2, Platform 2, Track 3. The third photo is looking outbound. From left to right you can see Track 3, Platform 2, Track 2, Track 1, and Platform 1.
Finally, a remote station with only inbound and outbound commuter tracks, and freight tracks on the side. The first picture is looking inbound, the second is of the same two platforms and two commuter tracks looking outbound.