Spinning ~ These guides have a larger ring size and start out large near the reel and end up being small at the tip. This allows the fishing line to flow off the spinning reel through the guides with less restriction and further more accurate casting.
Casting ~ These guides are generally used for baitcasting reels and the ring sizes change very little since the bait casting reel feeds the line straight off the reel through the guides.
Roller ~ These guides are normally used for much larger lb class fishing. These rods are put under a lot of stress and pressure is put on the fishing line. There are rollers that the fishing line is guided on to allow a smooth drag pull when a several hundred pound fish is peeling drag. It is a must for Tuna and Marlin fishing; however there are some lightweight rollers for the serious light tackle offshore anglers for Dolphin, sailfish, Kingfish, etc.
Quality of guides
Metal Guides w/Ceramic inserts - Economic in cost
Metal Silicon Carbide or SILGuides - (Top quality) Guide works well with braided fishing lines
All Metal Guides - A general-purpose guide
Roller guides - for heavy monofilament lines (30 lb class & up)
Hardened Roller Guides - for heavy duty (80 – 130 lb) class and wire fishing line (Top Quality)
Rods | Guides | Handles | Reels