These descriptions are listed here as they do not appear in the 2nd Ed PHB. The descriptions are taken from the Player's Option: Combat & Tactics book.
 
Back-and-breast. (AC 6; enc. none; type plate) This armor is simply a steel breastplate and back piece, worn like a shirt. It protects the wearer's vital organs but leaves the limbs uncovered.
Chain hauberk. (AC 6; enc. light; type mail) Chain mail was first constructed in Roman times as shirts or skirts. Throughout the Dark Ages mail was reserved only for the wealthiest warriors. By the end of the Dark Ages, the most common form of mail was the hauberk, a long-sleeved coat that hung to the wearer's knees. Because the lower legs are vulnerable, the hauberk doesn't offer the same protection that a full suit of chain mail does.
Chain-lamellar. (AC 4; enc. light; type mail) Chain mail was used widely in Byzantium and eastern lands, too. It was common for eastern peoples to augment their lighter mail with heavier armor. Chain mail with lamellar breastplates, greaves, and arm guards was widely used by Byzantine, Turkish, and Persian cavalry.
Cord Armor. (AC 8; enc. none; type leather) Cord armor consists of rope-like fibers woven and knotted into a thick, tough fabric. It may be found in places where leather is scarce.
Hoplite armor. (AC 5; enc. light; type plate) The armor of the classic Greek warrior consisted of a bronze breastplate and greaves with a studded leather skirt. It offered a good compromise of protection for vital areas without too much weight. Alexander's soldiers conquered half the world in armor like this.
Improved mail. (AC 4; enc. light; type mail) Several varieties of improved chain mail appeared during the Crusades. Bar mail consisted of small metal strips threaded through the links; double mail used heavier links double-joined; augmented mail used a thick leather backing to reinforce the coat. All types of improved mail offer better protection than normal chain mail, but at the price of increased weight.
Lamellar. (AC 5; enc. light; type mail) Lamellar armor consists of small, overlapping plates of metal sewn together or stitched to a backing of leather or cloth. It is similar to brigandine and splinted mail, but isn't sandwiched in leather like the other two armors. Lamellar is a very ancient armor that was used in Mesopotamia and ancient Egypt thousands of years before the rise of Rome. Byzantine and Persian cavalrymen used breastplates of steel lamellar as part of their heavy armor.
Lamellar shirt. (AC 7; enc. none; type mail) Full suits of lamellar armor were very rare in the Bronze Age, but lamellar coats with cloth skirts were somewhat more common. This composite armor represents the best protection available to the common soldier in extremely ancient settings.
Lorica hamata. (AC 6; enc. none; type mail) This Roman armor consisted of a chain mail shirt and a skirt of leather reinforced with bronze or iron strips. It was an early armor used from the time of the Punic Wars into the 1st century A.D.
Lorica segmenta. (AC 5; enc. none; type mail) Lorica segmenta replaced lorica hamata and was used until about A.D. 350. It consists of a breastplate of banded mail and a reinforced skirt of studded leather armor.
Mail and plate. (AC 4; enc light; type plate) Plate armor first appeared near the end of the Crusades as reinforcement for chain mail armor. Small breastplates were introduced first, but rapidly grew into full breast plates with complete leg and arm covering. The mail and plate armor describes an early form of plate mail in which a breastplate is worn over a full suit of chainmail.