A sheitel is a wig worn by Orthodox Jewish women to cover their hair.
There are many good reasons why a Jewish woman should shave her head when she marries. One explanation is that, during mikvah, water must touch every part of the woman's body. If the hair is knotted, water might not touch everything, and would render the mikvah invalid. So, best to shave completely!
Another reason is that we want to keep our wives under control, so they should not be tempted by contemporary culture. Shaving her head makes our wives less attractive.
Also, if a Jewish wife commits adultery, she must be humiliated by exposing her hair. Completely shaving the head is good incentive not to cheat, because what woman wants to reveal her bald head?
Incidentally, Jewish women and their pubic regions may be a hairy subject, but the topic certainly has been discussed.
Sheitel, sheital, shaitel ...