Gear ratio is the number of teeth on the following gear divided by the number of teeth on the driving gear (the gear inputting the motion).
A low gear ratio = more speed = less force
A high gear ratio = less speed = more force
Look at the gears in the diagrams below.
There are 18 teeth on the driver gear and 8 on the follower gear. The gear ratio would be 8/18 or 4/9. For every 4 turns of the driver, the follower turns 9 times.

If the gear and driver are switched. The gear ratio increases. The gear ratio would now be 18/8 or 9/4. For every 9 turns of the driver the follower will make 4 complete rotations.
This gear design would be good for multiplying force, not speed.