This is a term used to reference a football field. When looking at a field with all the lines from a top perspective, it is said to look like a gridiron in which foods are grilled on, which is metal grade of parallel bars.
The NFL and CFL both have different size football fields. In the NFL the teams must travel 100 yards to score a touchdown whereas the CFL is 110 yards. The NFL has 10 yard end zones, and the CFL has 20 yard deep end zones.