A tire's contact patch is the area of the tire that comes in contact with the ground, much like a footprint. Believe it or not, most tires have a fairly small contact patch -- a little larger than the size of your hand. As a result, not much of the tire's surface area is touching the ground, so the amount that does touch the ground must handle a great deal of weight and force.
The contact patch will vary in shape and size depending on the geometry of the tire, and this affects various performance characteristics of the tire. Tires with a higher profile or aspect ratio (that is, the height of the sidewall is fairly large compared to the width of the tire), tend to have a long and narrow contact patch. Typically, these would be tires made for passenger cars and light trucks. The longer, narrower contact patch gives these tires a smooth ride and allows them to handle in a predictable manner. They may also have especially good traction in snowy conditions.
Conversely, most high-performance and ultra-high performance tires have a lower profile (lower aspect ratio). As a result, the contact patch is generally shorter and wider, which gives them strong cornering stability and traction. This allows high-performance and ultra-high performance vehicles to have very responsive handling, especially on dry roads.