We don't know a ton about the specifics of Inscription and the Glyphs it supplies since the Wrath beta doesn't have very many of them yet, but we at least know what they are. If you don't know what they are, glyphs are almost like enchantments, but for your spells instead of your armor and weapons. Their effects are usually a little more substantial, even if they don't change combat very much. You're allowed up to six glyphs, split amongst the varying strengths of glyphs in a configuration that may or may not be the same come retail.
We got a litlte preview of glyphs via some Druid glyphs that were posted on MMO Champion a few days ago, and they do some pretty neat things. Things like "your Swipe ability now hits 1 additional target" and "changes the appearance of your bear and dire bear forms to that of a polar bear" are both pretty big effects! That's only really the beginning of them, too.
Pulling a little inspiration from our friend Matticus, why don't we take a minute and make a few guesses at what types of glyphs our classes will get? Heck, even if it's unlikely we'll get it, what type of glyph would you like to get? Personally, I'm holding out for "Glyph of It's About Time - Increases the range on Mind Flay to 30 yards" for my Shadow Priest. A guy can hope, eh?