The MTB, Mountain Bike, is designed for sporting use on rough tracks and terrain.
The majority of MTBs are semi-rigid (because of the suspension fork). The high-end MTB is fully suspended.
The better equipped the MTB (suspension, derailleur, braking), the more committed the use.
This bike is usually fitted with studded tyres and suspension, and the rider's stance is a sporty, leaning forward position.