Fitment is the confirmation of a series of specifications that confirm a wheel will fit a given vehicle.
Fitment specifications include, but are not limited to:
Frontspace
Backspace
Wheel Diameter
Wheel Width
Lug Pattern (or Pitch Circle Diameter)
Hub Bore Diameter / Center Bore
Load Rating (or Rated Weight Capacity)
Brake Clearance
Those wheel fitment specifications must either meet or exceed the specifications for the vehicle in question, depending on the particular description of the value in question.