A measurement of digital information storage or transmission, and a multiple of the unit "bit" using the International System of Units prefix.
The petabit is 10^15 bits, or 1,000,000,000,000,000 bits or 1000 terabits. A petabit is equal to 125 terabytes.
Petabits have no practical applications as of 2011.
Very similar to pebibits, which use a more exact prefix established by the International Electrotechnical Commission.