Answer:
A terabyte is one trillion bytes (1012 = 1,000,000,000,000 bytes) in current standard usage.
1 terabyte (TB) = 1,000 gigabytes (GB) = 1,000,000 megabytes (MB)
(There is a similar unit, the terabinary byte, or "tebibyte", which is 240 or 10244 = 1,099,511,627,776 bytes. However, this unit is never actually used, as hard drives are the only things that can hold this much, and they are always measured in powers of 10.)