Dental crowns and Porcelain Veneers are both types of dental restorations. Dental crowns are very strong and are often utilized in rebuilding teeth that are badly broken and decayed due to significant tooth abuse. The downside of this is that it requires tooth reduction and when a crown has been made for a tooth, that particular tooth will always require a dental crown. Porcelain Veneers

Source: Animated Teeth here

Tooth bonding can be used for cosmetic purposes. A veneering of dental bonding can enhance the appearance of a tooth that is partly stained or discolored. Bonding can also used to close teeth gaps and to reshape and re-align teeth that have little imperfection such as chipping and misalignment.

Another use of tooth bonding is for creating composite fillings. The restorative used in tooth bonding, or the dental composite, is also the material used for making natural tooth-colored fillings. This is a good alternative to silver fillings because the former is less noticeable.

Source: My New Smile

Direct restorations are the most common restorations. They refer to fillings that are consisted of dental amalgam or silver fillings, glass ionomers and resin ionomers or white fillings. These are then placed into a prepared cavity. This procedure is done in only one visit to the dentist. On the other hand, Indirect restorations are custom made fillings in dental laboratories, according to the prescription made by the dentist. The actual procedure may be finished in two visits. Indirect restoration is more expensive than direct restorations since the former consists of a more complex (at least for me) layer of inlays, onlays, dental crowns, and bridges.