A terabyte is 1012 or 1,000,000,000,000 bytes.
One terabyte (abbreviated "TB") is equal to 1,000 gigabytes and precedes the petabyte unit of measurement. While a terabyte is exactly 1 trillion bytes, in some cases terabytes and tebibytes are used synonymously, though a tebibyte actually contains 1,099,511,627,776 bytes (1,024 gibibytes).
Terabytes are most often used to measure the storage capacity of large storage devices. While hard drives were measured in gigabytes for many years, around 2007, consumer hard drives reached a capacity of one terabyte. Now, all hard drives that have a capacity of 1,000 GB or more are measured in terabytes. For example, a typical internal HDD may hold 2 TB of data. Some servers and high-end workstations that contain multiple hard drives may have a total storage capacity of over 10 TB.
Terabytes are also used to measure bandwidth, or data transferred in a specific amount of time. For example, a Web host may limit a shared hosting client's bandwidth to 2 terabytes per month. Dedicated servers often have higher bandwidth limits, such as 10 TB/mo or more.