Fixed orthodontic braces provide a very versatile treatment for a patient, as they allow the orthodontist to apply a wide range of forces to a tooth - not only the size of the force, but the direction as well.
In the early days of fixed orthodontic braces, this involved a tight fitting metal band being placed around the teeth and fixed with dental cement (and some very early bands were tightened onto the teeth with miniature screws).
The band would have a bracket attached to it before it was cemented onto a tooth.
This process was called "banding" These orthodontic bands were very reliably attached to the teeth, but also had many problems for the patient:

1. in order for the bands to attach securely, they had to go around the entire tooth, which meant pushing neighbouring teeth apart far enough to get a band on- usually two bands, one on each neighbouring tooth
2. pushing so many teeth apart far enough can be uncomfortable
3. pushing the teeth apart can also take several days, which makes treatment slower at the start
4. because the band covers much of the tooth it can be difficult to see if the tooth remains healthy underneath it as treatment goes on
5. when the bands are on the teeth, they cover so much of the teeth with metal it doesn't look too good (in the early days of orthodontics these bands were on the front teeth too)
6. because there is a huge variation in the shapes and sizes of teeth, the bands rarely fit the tooth exactly
7. when a band goes on it at its best fit, the bracket on it may not be at an ideal angle or position to connect with the wire that connects to all the other teeth in the orthodontic brace - this makes the treatment more difficult to get right
8. when the brace treatment is complete, all the bands have to be removed, which can be uncomfortable
9. when all the bands are removed, then the remnants of the cement that held them in has to be removed
10. when all the bands are removed there remains a certain amount of spacing between the teeth (depending on the thickness of the bands) - this can be dealt with, but takes another appliance

Nowadays, advances in dental science have developed very reliable special dental glues (called composite adhesives) that allow the fixed brace brackets to be attached directly on to the teeth, and banding usually only takes place on the back teeth if there are bands used at all.