All are used to hide the rider or trainer'a mistakes.
It depends on what your horse needs. If you have a horse that flips their tongue over the bit, you may need a regular noseband with a flash attachment (a simple noseband with a small strap in front of the bit). If your horse opens their mouth really wide when you apply bit pressure, a simple noseband that fits relatively snug will help. If you have a horse that plays with bit a lot, you can use a low noseband (the noseband sits in front of the bit, holding the bit in the groove).
You can also get nosebands that have rope, which increases pressure on the face. It also depends on what discipline you ride. Generally, a hunter would have a simple noseband. Dressage riders use a dressage bridle (thick noseband with a flash).
Openly speaking, a noseband is used to keep the mouth closed. You may need one, or may not. Always use the two finger rule, and give them some space to move their jaw or it may cause tension and result in them not giving to the bit as easily.