The mountain gear option for your bike can be used when cycling in a hilly or mountainous area. In these areas, you need a lighter gear ratio to make cycling in the mountains easier. With a lighter gear ratio, you cover less distance per rotation. This makes cycling on a hill or mountain easier. An ideal gear ratio is when you can achieve at least 60 rotations of the pedals per minute. Therefore, you have a more powerful drive through the mountain gears, but less speed with the same number of rotations. In the case of mountain gear on your bicycle, you have to make some concessions in terms of speed to get the gear ratio to work properly.
The mountain gear option is very suitable if you have little strength or high weight. Cycling in hilly areas then becomes easier.