A Coat of Arms (sometimes erroneously referred to as a Family Crest) is a heraldic design, which originated in Europe. The designs vary greatly (with a complex system on how each is to be designed) but generally, an arms is made up of a Shield in the center (painted in various colors) with two animal or human figures, known as "Supporters", on each side. On top of the shield is a Helmet (the style of which reflects the bearer's rank) out of which comes the Crest (see photo for detail).
Historically, an Arms was worn on tunics, shields, and other armorial accessories by lords and knights on the battlefield to distinguish allies from enemies (at this time, uniforms were not worn in battle). As time went on, members of the socially elite no longer used them simply in battle, but as social symbols.
Often times, those new to genealogy wonder whether or not there may be a Coat of Arms attached to their own surname. The fact is there are many misconceptions when it comes to Coats of Arms. First, not every family had a Coat of Arms. In fact, a Coat of Arms is not awarded to a family at all, but an individual, and is passed down from father to son, like a title of Nobility (wives and daughters could also bear arms modified to indicate their relation to the current holder of the arms). A proper authority on behalf of the monarch can only award arms.
There are many sites which claim to have your family Coat of Arms on file, and while these sites can be interesting in that they may indeed have a Coat of Arms one time born by someone who share's your surname, there is no guarantee you have any relation to that person. It is not recommended you make any purchases from sites such as these.
Also, on a final note, it is worth saying that after Monarchy was abolished in Italy in 1946, Heraldic Coats of Arms (known in Italy as Stemma) are no longer used, and has no legal value (as opposed to such countries as the United Kingdom).
It's my hope this article will help those interested in tracing their ancestry sort out misconceptions relating to this topic.