Dental bonding is a process by which a restoration is chemically and mechanically glued to the surface of the teeth. It is used in many dental applications (as we’ll explain in a bit), but it is usually concerned with composite resin (AKA the white colored tooth filling) and is often named composite bonding as well.

The process starts by preparing the tooth for composite resin bonding, which goes as follows:

Preserving the outer layer of the teeth (known as the enamel) is essential for a strong bond. Therefore, very minimal preparation of the tooth structure is needed (unless of course there is decay that needs to be removed).

After that, the edges are smoothened with a fine stone using the turbine.

An acidic material is placed on the prepared surface, creating micro roughness of that surface, which aids in the bonding.

The surface is cleaned and dried, and the bonding agent (a clear liquid) is applied to the area to be bonded. A strong light source is used to cure that bonding agent in preparation to receive the composite resin.

The composite resin is applied (after selecting the proper shade and color) and shaped with specialized instruments to accurately replicate the lost part of the tooth. Alternatively, a resin cement can be applied in cases of indirect restorations. Curing is done with the same light source as before.

The applied material is finished and polished

As we explained, the procedure of composite resin bonding and bonding a veneer (or any indirect restoration) is pretty much the same. The same acidic material is needed for etching and forming the micro roughness, the same clear liquid bonding material is used, and even the resin cement is the same material as the composite filling. The key difference is the amount of preparation needed before the restoration is placed, meaning how much of tooth structure must be removed (and subsequently, how much is preserved).
There is no right or wrong here, it all depends on what you need from your treatment, and what your dentist advises. If you only need to fill a minor gap or replace a small chipped part, then conservation of tooth structure is indicated and it is better to go for teeth bonding. On the other hand, if the lost part of the tooth is so large, making the replacement composite subjected to massive stresses, or if the teeth are so discolored or disfigured that a small layer of composite resin cannot possibly hope to provide a good appearance, then veneers are the right choice here.
Your dentist is best equipped to give you the best advice after carefully reviewing the situation.

Usually, a bonded restoration can last up to 5 years. Many factors affect that period such as eating habits, the way your teeth bite together, as well as smoking or drinking which can reduce that period significantly.

It is an artificial material that is not affected by teeth whitening. It can however be polished to regain some of its shine after a few months or years of usage.

If you are planning of having your teeth whitened, then yes you should do so before teeth bonding for proper shade and color matching.