If you can trace your lineage back to Scotland, France, England or most any European country, you might have a family crest. This is not to say that you can use this crest in any official capacity–only the monarch-approved Knight, Count or Duke (or what have you) retains the actual ownership of the crest. These are the people who descend directly from the original families.
But, it’s still worth the research. I have a friend in England who researched his crest and found that he did indeed have direct lineage of the Knighthood associated with it. Keep in mind, he had to spend years researching and petitioning the Queen (and then thousands of pounds buying the license), but he eventually got the rights and now plasters the emblem on his Bentley.
To be precise, the crest is actually the very top part of the official family Coat of Arms. It sits on top of a helmet, which in turn sits on top of a shield. Here is more info from Wikipedia, and this site tells you what each of the components means.
So, how do you go about finding your family crest? If you’re just looking for information, you can consult any number of online family-crest finders. Or, you can let the John Christian Company do the work.
When you order one of their family crest products (including cuff links, family crest rings and pendants) their researchers and jewelers do the research based on your name and country of origin, present you with a drawing for approval, and engrave your family crest in 14k gold, 18k gold, white gold or platinum. And this is what it looks like: