The Gigabyte is the equivalent of 1024 megabytes. The giga prefix originates from a Greek word meaning giant. Often, manufacturers of storage devices use the term to compare the cost per gigabyte of different units sold. Something similar, to what we do in the supermarket, when we are analyzing two similar products served in packages with different volumes. In these cases we compare the cost per pound to find out which one is best. This is a very common term used these days when we refer to disk space or storage drive. One gigabyte lets you store approximately the contents of several books used to fill a shelf about 10 feet long.
The Terabyte is the equivalent of 1024 gigabytes. The tera prefix originates from a Greek word meaning monster. The first 1 terabyte disk was a landmark in information technology. At the time of the release, the company Hitachi noted that it took 35 years to have 1 gygabyte, 14 years to have 500 gigabyte disks, but only 2 years to reach the terabyte. A 1 TB disc can hold about 5 million images or about 300 hours of medium quality video. Approximately 1,500 CDs are required to store the equivalent of one terabyte. Discs with this capability can store more than 1,000 copies of the "Encyclopedia Britannica". Some scientists estimate that our brain's memory capacity is around 1.25 TB.