Gears are an important part when building your robot because they allow you to mechanically adjust the performance of your robot. If you want a mechanism on your robot to spin faster then you need to build a gear train that has gears going from large to small. If you need more torque then what your standard motors can lift you will need to create a gear train that goes from small to large.

Here a 12 tooth gear is rotating a 60 tooth gear this will result in an increase in torque by 5
Here a 12 tooth gear is rotating a 60 tooth gear this will result in an increase in torque by 5
Here a 60 tooth gear is rotating a 12 tooth gear this will result in an increase in speed by 5
Here a 60 tooth gear is rotating a 12 tooth gear this will result in an increase in speed by 5
gear ratios