A unit of measuring data size. It is either 1,000,000,000 or 1024 megabytes, depending on how your computer reads it. A DVD can handle 4.7 gigabytes. A blu-ray disc can handle 25.
Basically, the more gigabytes your hard drive can take, the more porn you can shove on it.
(Comp Sci.)
A measure of computer memory or disk space consisting of about one thousand million bytes (a thousand megabytes). The actual value is 1,073,741,824 bytes (1,024 megabytes).