CROWN

A crown is a restoration that provides full coverage of your tooth (think of it as a cap on your tooth) and is used to help strengthen a tooth that is prone to fracture either due to an existing crack, or a large existing filling. It is also useful in restoring teeth that have had a root canal.  A crown is matched to the shade of the rest of your teeth in order to give a natural appearance.  A crown aids in keeping the jaw and bite aligned, prevents shifting of other teeth, and bears the forces from biting and chewing. 

BRIDGE

A bridge is used to replace one or multiple teeth.  It is usually anchored to the teeth on either side of the space.  The teeth being used as anchors usually have crowns placed on top of them as well.  A bridge commonly consists of a fake tooth (or teeth) in the centre and have crowns attached on either side.  The entire bridge is cemented in place and the fake tooth (or teeth) sits on top of the gums to give the illusion of a real tooth, or multiple teeth emerging from the gums.  Bridges come in various materials such as porcelain (matched to the shade of your existing teeth) or gold.