That's a pretty common question. Even though the high-resolution photos on KnivesShipFree do a good job of showing the difference between the two finishes, it occurs to us that an explanation (and a couple of side-by-side comparisons) would be helpful.
The standard finish used on Micarta and G-10 by Bark River Knives (for example) involves polishing the material with very fine grit, followed by applying a wax compound to the surface and buffing it to a gloss.
A matte finish is accomplished by ending the polishing process a bit sooner, finishing with somewhat coarser grit. No wax is used.
Most folks who try both finishes develop a preference, one way or the other, based either on appearance or (perceived) grip. To start with, we'll focus on appearance.
First, here's what a matte finish looks like on black linen Micarta, compared to a standard finish (below).
As you'd expect, the matte finish isn't as shiny. You'll also notice that matte-black Micarta is somewhat grayish compared to the standard finish.
On other colors -- like green G-10 and maroon Micarta -- the color difference between the two finishes is much more striking. Perhaps the most dramatic shift is with natural canvas Micarta (below).
Although we've shown these finishes as they appear on Micarta, you'll see comparable differences on G-10.
A word about grip
You're probably guessing that a matte finish is "grippier" than a glossy standard finish. And you'd be right -- up to a point.
The difference in grip isn't nearly as great as you might think. For practical purposes, they're pretty much the same.
Micarta and G-10 knife handles are smooth, regardless of finish. That's a good thing, because the grippier the handle, the more likely it is to give you "hot spots" in prolonged use.
A properly designed knife handle moves in the hand. Grip comes from the handle's ergonomic shape, not from its finish or material.
Changing the finish
Let's say you try the standard finish and find yourself wishing for matte. You can make that happen yourself -- use a Scotch-Brite pad and some grease-cutting dishwashing liquid, and gently scrub the surface to a finish you like better.
As an alternative, of if you want an even grippier finish, you can use 400-grit sandpaper.
Go slowly, adjusting your handle's finish a little at a time. Don't use steel wool, and don't soak your knife in water (soapy or otherwise).
On the other hand, if you have a matte handle and decide you'd like to try a glossier finish, apply some paste-type car wax and buff away.
Finally, if you own a Bark River knife and you're not much of a do-it-yourselfer, you always have the option of sending it to the Bark River Spa.