Just one of many new "Terabyte Drives" that are here, or coming -- and coming down in price (generally in the $200-500 range, depending on size and brand).
Get used to seeing TB instead of GB, just as GB replaced MB as the HD (hard drive) standard.
A TeraByte is a thousand GigaBytes, or a million MegaBytes! That's a Mega-MegaByte!
In other words: 1000 MB = 1 GB, and 1000 GB = 1 TB. Yep, TB is the new GB.