FPS means Frames Per Second, and it`s value is used to know how good your system is performing certain graphical tasks.
A high FPS value usually means smooth animations, scrolling, etc... while a low value is the result of a sluggish, choppy performance. The more complex the task is, the lower the value will be.
Games that use 3d animations, including several lightning effects, textures and quick variations in the camera angle are a good way to test your system.
Please mind im way far from being an expert in the topic, so if there`s anyone out there who would explain this in a better way, feel free to do it and correct me as much as possible.
Sadly, I don`t know how to make the game show the FPS, nor if the feature is even included.
Though I`d try using the console, and typing the first part of the would-be command, and then pressing Tab to see if the program fills in with the remaining part... It works with some games... anyway, its just a guess, so wish you good luck