Crests are the Symbols above the helmet.  It is a part of a Coat of Arms.

So what is a crest? Simply, a crest was worn above the knights helmets because the shields were difficult to see in the heat of battle. They helped to further identify the knight. Today they are a part of the coat of arms as we know them.

The crest is placed on top of the helmet. The history of the crests is somewhat obscure. Most early coats of arms had no crest, and those that do are probably of a later time. In heraldry of some nations, the crest is absent and only a plain helmet is employed. It is also common to find the main charge of the shield used as the symbol of the crest.