The term "crest" is used interchangeably with "coat of arms," but there is a difference. A crest is a small image on the top of a helmet. Coat of Arms refers to the shield, crest, helmet, mantling and supporters. It also has the surname of the individual it was originally bestowed upon. It's easy and free to find yours online.
Search for the history and origin of your surname at websites such as Ancestry.com and The Internet Surname Database. A search of the surname at FamilySearch.org will display historical records of individuals with that name. Surname records are also available in the Genealogy department at the local library.
Look at images of the crest at sites such as AllFamilyCrests.com and HouseofNames.com. HouseofNames also has a some paragraphs about the surname history and origin, but you have to pay if you want to know more.
Enter the surname into the search box of the crest site. If your family has a crest, the results will include its image. Depending on the website, the search results will also tell you the origin of the surname and possible alternate spellings.