A coat of arms, or family crest, originates from heraldic arms or armorial signs that were worn by soldiers or fighters belonging to a particular family or group of people in the Middle Ages. They tended to be used by knights and nobles to indicate their allegiance in war and to distinguish themselves from enemy soldiers. Over time these crests lost their strictly military associations and were used by families, regions and various institutions.
A coat of arms creator is a service available on certain websites that let you design your own coat of arms based on a series of parameters which determine the colors, patterns and images that are used. In the past, elements of a crest or coat of arms would have been chosen based on the attributes of the person commissioning them. When making your own crest you can choose these attributes for yourself from multiple options, choosing the text that will appear on it and the website will generate the crest for you automatically.