The contact patch refers to the area of the wheel that actually makes contact with the ground. The wider the patch the more grip you will have due to the larger surface area touching the ground. Wheel shape can determine the contact patch, round wheels found on street boards will have a smaller contact patch due to the rounded edges than say, longboard wheels which are typically square in shape.
The contact patch will determine the speed at which the wheel rolls. This is due to the level of resistance with the ground, wider wheels with a large contact patch will experience more friction with the ground, ultimately slowing them down. Large wheels often offer a smoother ride because the larger surface area can absorb lumps and bumps a little better than those with a small contact patch.
