Welcome to Como Lake Village Dental Centre
A bridge replaces lost teeth. The dental laboratory makes the bridge in one piece, but it usually has three components or "units"  
The units on each end of the bridge are the crowns or "caps" that sit over top of the teeth which still exist on either side of the missing tooth. These crowns hold the bridge in place, or retain it. So they are known as the retainers. The units in the middle which replace the missing tooth or teeth are called pontics.  
The two crowns will be permanently cemented into place and this will keep the bridge in the mouth. Another option for replacing missing teeth is to use a denture. A denture is not permanently cemented and can be taken out. When a denture replaces all of the teeth on the top or bottom of the mouth it is called a complete denture. If the person still has some of their own teeth, then a partial denture would be made.  
The third option for replacing a missing tooth, or missing teeth, is to use a dental implant. A titanium post, or implant, is inserted into the jawbone and a porcelain crown is placed on top. An implant is the closest option to having your own tooth back, but will cost a bit more than a bridge.