Kevlar vest

A ballistic vest or bullet-resistant vest, often called a bulletproof vest, is an item of personal armor that helps absorb the impact and reduce or stop penetration to the body from firearm-fired projectiles- and shrapnel from explosions, and is worn on the torso. Soft vests are made of many layers of woven or laminated fibers and can protect the wearer from small-caliber handgun and shotgun projectiles, and small fragments from explosives such as hand grenades.

These vests often have a ballistic plate inserted into the vest. Metal or ceramic plates can be used with a soft vest, providing additional protection against rifle rounds, and metallic components or tightly woven fiber layers can give soft armour resistance to stab and slash attacks from knives and similar close-quarter weapons. Soft vests are commonly worn by police forces, private citizens who are at risk of being shot (e.g., national leaders), security guards, and bodyguards, whereas hard-plate reinforced vests are mainly worn by combat soldiers, police tactical units, and hostage rescue teams.

Body armor may combine a ballistic vest with other items of protective clothing, such as a combat helmet. Vests intended for police and military use may also include ballistic shoulder and side protection armor components, and bomb disposal officers wear heavy armor and helmets with face visors and spine protection.

Ballistic vests use layers of very strong fibers to "catch" and deform a bullet, mushrooming it into a dish shape, and spreading its force over a larger portion of the vest fiber. The vest absorbs the energy from the deforming bullet, bringing it to a stop before it can completely penetrate the textile matrix. Some layers may be penetrated but as the bullet deforms, the energy is absorbed by a larger and larger fiber area.

...
Wikipedia