Protection from weapons for the body. Armour has been around as long as man has been whacking man with weapons. Armour in the west/europe evolved as weapons evolved to defeat the protection.
In the classical period (150bc), body armour was made of bronze. For the greek Hoplite (the nailsest for the period) his armour consisted of a bronze breastplate and bronze shin guards (called greaves). The armour was pretty effective at stopping blows from bronze swords and spears. Swords would often bend and the spears broke so often on hitting the armour that they had a back up spike on the butt end so you weren't left holding a stick in the middle of an F off melee.
Roman armour was made of iron. Firstly metal rings linked together into a shirt (called chainmail) which stopped edged weapons (ie gaullic slashing swords) but was F all use against arrows or spears since its mostly holes and doesn't stop the thrust. Still proved very popular. Other armour was made of plates called Lorica segmentata. Very efficient and appears in every movie about Romans even though it only lasted in service 150ish or so years.
Lots of chainmail and steel forearm protection called vambraces.
Started out with lots of chainmail but soon the race between weapon and armour began. Armour began to get heavier, include plates of steel and in general stopped edged weapons. Slashing edged weapons like the sword evolved into swords that were designed to thrust and exploit gaps in the plates. Other weapons like the mace, flail and polearm evolved from peasant weapons to crush the heavier armours. Medieval armour reached the end with full plate, could evolve no more and the emerging firearm made such armour obsolete in the space of less than 100 years.
Armour started to vanish off the battlefield since it no longer protected and there was no point being weighted down by something that did F all good. First it reduced to breastplates for heavy infantry (i.e. pikemen) and shock cavalry until by the late 17th century only cavalry had any.
Only the elite cavalry clung to their breastplates like the British Lifeguards or French cuirassiers. There was hot debate as to whither the armour was any bloody use (although it would stop a pistol ball and deflect the odd musket ball). The cuirass (chest armour) vanished after the end of the Napoleonic era except for ceremonial purposes i.e. trooping of the colours.
Armies in medieval conditions experiment with plate armour. Steel plate body armour is trialed with helmets and face vistors but binned because its too heavy to wear and not that effective against a 5.9" shell. As a Subaltern Roland Boys Bradford VC, the boy wonder CO experiments with lightweight aluminium armour but is disappointed to discover its not bullet proof. Chainmail (remember the metal rings linked together) makes a reappearance for tank crews to protect their hands and face/head from spaulling (bits of metal from inside the tank coming off at high speed due to the tank being shot up).
Body Armour is mainly restricted to air crew. Shrapnel proof vests worn by USAAC air gunners give name to post war body armour - "Flak Jackets" Other aircrew also tried to protect their genetic future commonly with some variety of armoured cricket box.
A heavy plastic waistcoat which makes you sweat and has the feel of a bag of wet straw, which is no suprise as body armour is actually filled with wet straw. Many studies have shown body armour to be an extremely effective life saver, not because of the protective properties of wet straw, but because it keeps all the bits in more of less the right place until someone can find an RAMC doctor to do the necessary - a task of hercules indeed.
In the 1980s a form of body armour was introduced for use in Northern Ireland, the INIBA which incorperated balistic plates and was worn under the combat jacket to look a little less obtrusive. More recently the CBA has been issued, similar to the INIBA but in a DPM cover and worn over the Combat 95 clothing.
Armamid and Kevlar
Soft body armour that contours the body like clothing. In the 1960s scientists realised certain synthetic fibers were extremely strong and light-weight. Someone then realised that placing layers of these aramids on top of each other created a ballistic resistance, while still remaining light-weight. Kevlar is one of the most effective "protective" materials used in body armour and is still be used in modern military body armour systems. They actually now call soft body armour a "bullet or stab proof vest" Like the ones seen at www.safeguardclothing.co.uk. Aramids are also sometimes used to make "hard armor plates" by way of a slightly different process.