Bio
Armor is the thick white suit that all or the majority of Clone Troopers and Stormtroopers wear. It helps protect them in combat, as well as in dangerous enviornments.
The actual armor made from thick metal, while the under armor is made of a thick latex material, which appears to be thin.
A diagram example of Clone Trooper armor.
Basics
There are three main Phases of armor, all of which consist of different versions and accessories. The actual armor suit, however, is made up of several parts:
Helmet- The main piece of armor that helps Clones breath, and see in certain enviornments; protects against most head-related dangers.
Front Torso Plate- The other main part of the armor, which helps protect against blaster bolts.
Rear Torso Plate (not shown in image)- Stores com-link scanner to communicate with troops and Republic officials from far away distances as well as storing a battery to power utilities and/or attachments (such as a rangefinder).
Utility Belt- Consists of different weapons and ammo for the Clones.
Thermal Detonator Case- Located on the rear of the utility belt.
Arm Gauntlets- Used for protecting the arms and providing a better grip for the Clones. Some (notably for Phase 1 and 2 Clones) include special wrist communicators for communicating from far distances on the battlefield, which are powered by a scanner located in the rear torso plate.
Shoulder Pads- Protect against having severe shoulder damage, as well as providing more comfort. Consists of upper and lower.
Rear Torso Plate- Contains small built-in communicator which helps power a small wrist communicator as well as helmet accessories, such as a range-finder.
An example of a thermal detonator container.
Flexible Cushion- Provided for movement comfort; connects the torso with the rest of the armor.
Crotch Plate- Connects the torso and leg armor together.
Thigh Gaunlets- Provides leg comfort for running in the battlefield.
Knee Pads- Provides comfort for the knees while running or kneeling.
Boots- Connects to the Knee Pads and Thigh Gaunlets.
Lower Boot Shoes- Connects to the rest of the leg armor.
Under Armor- Thin black jumpsuit, undersuit, bodyglove, or suit, used for supporting the actual Clone armor.
Sources
http://www.501st.com/crl/TK_CRL/122_Stormtrooper_HWT/index122.php
Trivia/Facts
Stormtrooper armor was often nickamed "plastic junk" or "scrap metal" from the Rebel Soldiers and numerous bounty hunters during the Galactic Civil War Era.