A crown (cap) is a restoration that is placed on teeth that have lost a lot of their structure.  There are various types of crowns, ranging from full porcelain to full metal.  Your dentist will explain the advantages and disadvantages of each kind for you.

A bridge is essentially a series of crowns that are connected to restore a missing tooth or number of teeth.

The process of making a crown includes a number of steps, beginning with preparing and taking impressions of the tooth/teeth involved.  A temporary crown or bridge is then placed on your teeth.  Meanwhile, the impressions are sent to the lab where a mold of the teeth is poured and the work begins.  The completed work is sent back to the office; after inspection and any necessary adjustments, it is cemented onto your teeth.