G-10 is a fiberglass weave bonded by eboxy. It is very strong, hard to scratch, hard to break. When bead blasted, it reveals the fiberglass strands (since the eboxy is worn away faster in the bead blasting) which leaves a rough, grippy surface. When polished, G-10 looks like carbon fiber (below). See Spyderco Manix, Al Mar SERE 2000.
Micarta isn't quite as strong as G-10, and it is easier to scratch, but it is still very strong. Micarta comes in three types: paper, liner, and canvas. These materials are layed with epoxy. Paper is the "weakest" and shows very little grain. It looks like a solid color. Linen Micarta is stonger and shows a wood-like grain. Canvas is the strongest and shows a weave-like pattern. Micarta is sort of like a more "classy" G-10 since it is very strong but looks a little nicer. Micarta is usually smooth, but can be bead blasted. Canvas Micarta takes a nice grippy finish when bead blasted. See various Bob Dozier knives, Ontario Hossom folders.
Carbon Fiber is a carbon (graphite) weave. It is very light and very hard, but it is brittle. When polished it is easy to scratch. It is a very nice looking material and has an almost holographic effect to it. It can be left rough and will be grippy but is more often polished to bring out the effect of the weave. G-10 looks similar when polished but is more often bead blasted because the material takes to bead blasting better and leaves a great grippy surface. See Benchmade Activator (polished black carbon fiber, grey polished G-10), Spyderco CF Military (not polished CF).
Zytel is a brandname of Fiberglass Reinforced Nylon (FRN). FRN is basically plastic. It is pretty tough stuff, and light, but it is easy to bend and is easier to break and deform than the above materials. See Spyderco Native, Benchmade Griptilian.
The top three materials are "premium". G-10 is probably the toughest overall, but Micarta and carbon fiber are often prefered for their looks and still very good strength. FRN is an inexpensive material usually used to be cost effective and deliver a lot of knife for the money.