A celebrity is a very famous person. If you single-handedly save an entire family from a burning building, you'll become a local celebrity.
Celebrity comes directly from the Latin celebritatum, meaning famous, and is related to the verb celebrate which means to honor something with the proper ritual. We usually use celebrity now when we talk about entertainment stars, but someone doesn't have to be on the supermarket tabloids to be a celebrity. Celebrity can also be used to mean the state of fame. If you are seeking celebrity, develop a thick skin for nasty rumors.