A fabrication is something made up, like a lie. Telling your boss that the subway broke down when in fact you just forgot to set your alarm is a fabrication.
The word fabrication was originally used to talk about manufacturing or construction, and it referred to the act of assembling something. Tires and steering wheels are necessary materials for automobile fabrication. Nowadays, the word fabrication is usually used to refer to the act of coming up with a story out of thin air. In this sense, a book of fiction is a fabrication, as is the lie you tell your girlfriend to explain why you forgot her birthday (again).