In children, treatment can be carried out with appliances, braces or aligners. When we fit braces, they are usually bonded to the surface of the permanent teeth that have already come through. In the early mixed dentition stage – that is, when the child is around 8–9 years old – the permanent teeth in the mouth are the four front incisors at the top and bottom and the back teeth, the first molars. The braces system used at this age is placed on these permanent teeth and is called 2 x 4, because it covers 4 teeth at the front and 2 teeth at the back in the same jaw. The aim of braces placed this way is to straighten the front teeth, using the back teeth as anchorage, while not being bonded to the baby teeth, which will soon become loose and fall out – so the braces don't get in the way of these teeth being replaced.
This answer is for general information. Your own case needs an examination by an orthodontist.