Gear ratio refers to how many turns of the spool or rotor you get for each full turn of the handle. If you turn the handle so that it completes one full turn and the spool makes 5.1 revolutions, the gear ratio is labeled 5.1:1. The gear ratio listed on the reel indicates how fast your retrieve will be. A 6.1:1 gear ratio retrieves the line faster than a 4.1:1 gear ratio. You might consider this to be important in situations where you are making many casts and covering a lot of water. A slower gear ratio, however, provides more power (as with a lower gear in a car). This could be considered important when fighting larger fish.