Mountain bikes have large, knobbly tyres for traction and a wide range of gears to help you get up and over mountains or across fields. Some models have front suspension, some have front and rear suspension, while others have neither.
Mountain bikes usually have 26", 27.5" (650B) or 29" wheels and have a frame geometry making them better suited for severely uneven ground. More expensive models have hydraulic disc brakes that significantly increase braking efficiency in any weather condition.
Mountain bikes are ideal for all off-road pursuits, but not recommended for going fast on tarmac roads or cycling long distances.