You've seen these two numbers before. For example: 5:1, 6:1, 7.2:1, etc. What do they mean, and how does this affect your fishing experience?
In the simplest of terms, a fishing reel is just a winch that is used to retrieve line. Reels convert a single turn of the handle into multiple turns around the spool. This allows an angler to quickly retrieve casted line in an organized manner.
In mechanical engineering terms, a winch with a ratio less than one will retriiee line very slowly, but it will be able to retrieve a lot of weight relative to the power used to turn the handle.
Consider a reel with a 1:10 gear ratio. This reel would require 10 turns of a handle for 1 full revolution around the spool. You have experienced this if you've ever winched a boat onto a trailer. You wouldn't want to reel in a fish that slowly, but if you did, you could reel in a very large fish with very little effort.
But fishing reels don't use gear ratios less than one, otherwise we'd spend all day reeling in just one fish. Instead, fishing reels use ratios greater than one, because we want to get that fish into the net before it has a chance to throw the hook or break the line.
A fishing reel with a ratio of 7:1 will turn 7 times around the spool for each turn of the handle.
You'll often see higher gear ratios on baitcasting reels, and there's a reason for that. Baitcasters are the preferred reel for ripping large bass out of heavy cover, and most anglers want to do that as fast as possible to minimize risk of losing the fish.
But a very high gear ratio isn't always the most desirable, because there are situations where a slower retrieve may make for a better lure presentation. For example, in cooler weather when fish are lethargic, you may want to try a slow retrieve, and a lower gear ratio may make your presentation appear more desirable to a fish that isn't very active.
If you have the capability to carry several rods or you just want to look like a professional bass fisherman, it makes sense to have several rods and reels with different gear ratios that work better for different types of lures. On the other hand, if you can only carry one rod, you may want to choose a reel with a high ratio. After all, it is easier to slow down the crank on a fast reel than it is to speed up the crank of a slow reel.