A terabyte is the same as saying 1 trillion bytes, or 1000 to the fourth power, or 10 to the twelfth power. Usually terabytes are used to describe the size of a hard disk drive in a computer. The first disk drive created that was at least 1 terabyte in size was made by Hitachi in 2007. In more recent years they have become rather commonplace and come pre-installed in many home computers and web servers.
As computer storage needs increase, the term terabyte will no doubt one day become a relic of the past like many other units of measure. For now the use of the word terabyte is most often applied to storage devices and in some cases, computer memory.