A French twist is a common "updo" hair

Hair

Hair is a filamentous biomaterial, that grows from follicles found in the dermis. Found exclusively in mammals, hair is one of the defining characteristics of the mammalian class....

 styling technique. It is created by gathering hair in a low ponytail

Ponytail

A ponytail is a hairstyle in which most or all of the hair on the head is pulled away from the face, gathered and secured at the back of the head with a hair tie, clip or similar device, and allowed to hang freely from that point. It gets its name from its resemblance to the undocked tail of a...

(not secured) and twisting the ponytail upwards until it turns in on itself against the head. It is then secured with pins, clips, sticks or a comb.

French twists are usually worn to proms and weddings when they are in a tight fashion; however, one could wear a messier, looser look to the office or out on the town. Hair clips are also commonly used with French twists.