A Matte finish is very flat and creamy - like the surface of paper. It doesn't reflect light. The benefit is it will usually give you more coverage, matte foundation or powder can give you a more flawless look, but it will be more obvious that you have make up on. A dewy finish would have a slight sheen to it, and reflect light, this will give you a fresher, less "made up" look and hi light your cheekbones and brow bones. Eye and lip colours are the same. You could have a very creamy lipstick with no shimmer or shine in it - that would be matte. and a lip gloss or sheer lipstick would be dewy. Matte makeup - especially matte lips are more associated with a vintage style of glamour. Dewy makeup is a younger, fresher look. Think shimmer rather than full on glitter. If you like strong colour - go for a strong eye or a strong lip, never both - it's too much. As for what's in style, they both are depending on what kind of look you want to achieve. I recommend you try i.d bare minerals - its a semi matte powder makeup but still very natural. You can build up as much coverage as you need and it comes in tons of shades. I would steer clear of matte eye shadows - it can look aging.