Armor is what keeps you alive and healthy. It comes in several types, in several styles, and of several different materials. The pieces are the Cuirass, Left Pauldron, Right Pauldron, Gauntlets, Greaves, Boots, Helmet and Shield.
Leather is the lowest protection available. Its cheap and plentiful. It provides +1 protection to whatever part of your body its covering.
Chain is the next highest protection. Its not quite as cheap as leather, nor quite as abundant, but its still easy to come by. It provides +3 protection.
Plate is the most diverse form of armor and where you can really get into style. In increasing order or protection, the materials are:
Your level and your Luck determine what the top-end material is for you. Orcish anything is extremely rare. Logically it would be Daedric since thats the top end, but at higher levels (15 to 17 and above) you find Daedric all over the place. If you can manage to put together an entire suit of Orcish plate (forget style - just find all 8 pieces), youre either very persistent or very lucky. Silver armor is available, but extremely rare. In over 2000 hours of playing time I have come across one set of boots, a left pauldron, a right pauldron and a set of gauntlets and a cuirass (that's one of each item).