A vest is a garment covering the upper body. The term has different meanings around the world:
Undershirt
(an undergarment, normally worn under a shirt)
It is known as an undershirt in the US, vest in the UK and many commonwealth countries, and singlet in Australia, and is typically in the form of a T-shirt or sleeveless top.
Waistcoat
(a sleeveless under-jacket)
This is called a waistcoat in the UK and many commonwealth countries, or a vest in the US. It is often worn as part of formal attire, or as the third piece of a lounge suit.
Other sleeveless jackets
Vest may refer to other outer garments, such as a sports tank top, or a padded sleeveless jacket popular for hunting, commonly known as a hunting vest. Another common variant is the fishing vest which carries a profusion of external pockets for carrying fishing tackle. The term jerkin is also used to refer to this sort of sleeveless outdoor coat.
A sweater vest (American English) or jumper (British English)
This may also be called a pullover, sleeveless sweater, or tank top (which may also refer to a type of sleeveless shirt).
Banyan
This Indian garment is commonly called a vest in Indian English. The term vest derives from French veste, Italian vesta, veste "robe, gown," and Latin vestis. The sleeveless garment worn by men beneath a coat may have been first popularised by King Charles II of England, since a diary entry by Pepys (October 8, 1666) records that "[t]he King hath yesterday, in Council, declared his resolution of setting a fashion for clothes.... It will be a vest,

The term vest derives from French veste, Italian vesta, veste "robe, gown," and Latin vestis. The sleeveless garment worn by men beneath a coat may have been first popularized by King Charles II of England, since a diary entry by Pepys (October 8, 1666) records that "[t]he King hath yesterday, in Council, declared his resolution of setting a fashion for clothes.... It will be a vest,
Different types of vest
A ballistic vest, bulletproof vest or bullet-resistant vest is an item of protective clothing that absorbs the impact from firearm-fired projectiles and shrapnel fragments from explosions. This protection is for the torso. Soft vests are made from many layers of woven or laminated fibers and protect wearers from projectiles fired from certain handguns, shotguns, and small fragments from explosives such as hand grenades.
A cooling vest or ice vest or "precool vest" is a piece of equipment worn to cool a person down. Cooling vests are used by many athletes, industry workers, doctors, and people with Multiple Sclerosis. Olympic athletes use the lightweight body cooling vest to pre-cool before events Vests range in weight from around two to eight pounds, depending on the model

Cowboy vest can be a casual piece, or it can be used to dress up an outfit for a night out on the town. When most of us think of Western wear, we think of rugged clothing in warm or rustic shades of brown, orange and black or green and turquoise for Southwestern attire. Leather, heavy cotton and even twill are all popular fabrics for Western clothing. Cowboy outfits are available in several colors and designs.
Lasso one of these western vests and complete your classy look, cowboy. You'll exude "elegant Texan," whether you're in New York, Paris, or Sundance Square. Perfect for weddings or a night on the town with your sweetheart.
Hunting vests are a necessary part of the dresses of the people going for hunting like fishing vests are of people going for fishing.