There are 5 major different styles of fishing reels and they are all used for different situations.
Bait-Casting Rods & Reels are the most common rods and reels that are used among most tournament bass fishermen. The reel is actually mounted to the top of the rod and this makes pitching and flipping a lot easier than with a spinning rod. The baitcaster rods and reels are also the top choice among many northern pike and muskie anglers. The reels are made to handle the heavier line that is required to cast heavier lures such as spoons, big crankbaits and big swimbaits.
Clicker Reels are great for fishing with live bait. These reels are set up so there is a very light drag when it is set up correctly. Once a fish bites, you will hear a clicking noise from the fish pulling line from the reel. All you have to do is push the lever to the appropriate position, then set the hook and the reel goes back to its normal drag settings. This way, you can set out a couple of bait rods without worrying about a fish pulling your rod into the water, snapping a line or just missing a bite. There are bait casting and spinner reels that are made with the clicker option.
Spinning Reels utilize a fixed spool that is normally mounted below the rod. They are typically used for lighter tackle such as live bait or smaller lures, however, with new technology and the creation of braided line, more and more anglers are using spinning tackle for bigger lures and bigger fish. Spinning reels also solved the problem of backlash, as they do not have a rotating spool to overrun and foul the line.
Spin-Casting Rods & Reels are made for using much lighter tackle and catching smaller fish. The rods have small eyes and typically a forefinger grip trigger. They are similar to bait casting rods, but the baitcaster rods and reels are made for handling much heavier tackle and bigger fish. Most of the anglers that use a spin casting rod & reel are new anglers and they are usually kids that are just learning how to fish.
Fly Fishing Reels are normally operated by stripping line off the reel with one hand, while casting the rod with the other hand. You can find fly reels for as cheap as $20 that will get the job done for panfish and upwards of $700 or more that are ideal for trophy freshwater and saltwater fish. Just like fly fishing rods, you should do your research before purchasing a fly fishing reel. As the quality goes up, the price goes up rapidly. If you are pursuing bigger fish, you are going to want a quality fly fishing reel.