A measurement of digital information storage or transmission, and a multiple of the unit "bit" using the International System of Units prefix.
The terabit is 10^12 bits, or 1,000,000,000,000 bits or 1000 gigabits. A terabit is equal to 125 gigabytes.
Terabits will likely only describe download and upload speeds for broadband, mobile data and dialup services as well as ethernet port speed in 5 years from now, as gigabit remains the fastest, currently.
For example, many ISPs will sell broadband packages of 15Mbit/s (megabits) downstream and 5Mbit/s upstream.
Therefore, to calculate how fast your actual download speeds will be, in bytes, you must divide those figures by 8. 15mbit/s = 1.875 MB (megabytes) per second.
Very similar to tebibits, which use a more exact prefix established by the International Electrotechnical Commission.