A measurement of digital information storage or transmission, and a multiple of the unit "byte" using the International System of Units prefix.
Zettabytes are 2^70, which is equal to 1,180,591,620,717,411,303,424 bytes when in relation to computer memory like RAM.
The ZB are also 10^21 or 1,000,000,000,000,000,000,000 bytes when in relation to storage solutions like flash drives or hard drives.
ZB are one of the largest measures of byte multiples and are never seen. That should change in the next few years as data continues to explode at exponential rates.
Very similar to Zebibytes, which use a more exact prefix established by the International Electrotechnical Commission.