A Mud Terrain Tyre is a type of automotive tire

Tire

A tire or tyre is a ring-shaped covering that fits around a wheel rim to protect it and enable better vehicle performance by providing a flexible cushion that absorbs shock while keeping the wheel in close contact with the ground...

 which may be fitted as an aftermarket

Aftermarket (automotive)

The automotive aftermarket is the secondary market of the automotive industry, concerned with the manufacturing, remanufacturing, distribution, retailing, and installation of all vehicle parts, chemicals, tools, equipment and accessories for light and heavy vehicles, after the sale of the...

 option to four wheel drive

Four Wheel Drive

The Four Wheel Drive Auto Company, more often known as Four Wheel Drive or just FWD, was founded in 1909 in Clintonville, Wisconsin, as the Badger Four-Wheel Drive Auto Company by Otto Zachow and William Besserdich.-History:...

 vehicles.

Mud terrain tires are characterized by large, chunky tread patterns

Tread

The tread of a tire or track refers to the rubber on its circumference that makes contact with the road. As tires are used, the tread is worn off, limiting its effectiveness in providing traction. A worn tire tread can often be retreaded. The word tread is often used incorrectly to refer to the...

designed to bite into muddy surfaces and provide grip. The large open design also allows mud to clear more quickly from between the lugs.

Depending on the composition and tread pattern, many mud terrain tires are not well suited to on-road use. They can be noisy at highway speeds, and due to the open tread design, they have less of a contact area with the road, limiting traction.