Body armour generally comes in two formats; soft or hard.
Soft armour is usually made from layers of specialist fabrics such as Kevlar or Dyneema. It is cut to body shape sizes that wrap around the body and can generally stop low calibre bullets, stab and spike threats.
Soft armour is genrally quite flexible so will contour to the shape of your body. Due to the number of layers required to stop a knife, spike or bullet, soft armour is usually reserved for lower energy projectiles.
It is quite common for the fabric layers to be mixed with other flexible materials or different grades of the same material in order to satisfy multiple threats, for example a handgun bullet and a knife.
Soft armour is most popular for civilian use including security guards, bodyguards, paramedics. As it is generally flexible, soft armour is also popular amongst local authorities and government organisations where the armour can be inserted into specially designed carriers or clothing such as jackets.
Hard armour has traditionally been made from ballistic steel or ceramic plates however technological advancements have meant more choices have appeared on the market including engineer plastics or boron carbide. Hard armour is usually cut into a SAPI plate, short for Small Arms Protective Insert. It covers the vital organs against stronger threats, such as rifle rounds. SAPI plates can also be made from soft armour.
The type of body armour you choose to wear is usually dictated by the task, threat and cost. Soft armour can protect a larger area of your body however the cost and weight of the vest may make it less attractive. Hard armour or a SAPI plate can protect less of your body however it is generally lighter and cheaper.
Some militaries use a combination of both armours. There has been an increase in the purchase and use of standalone SAPI plates due to the desire to protect the vital organs at an affordable price and evidence to suggest that the chest area is more commonly struck.