An exabyte is a collection of about 1 quintillion bytes, which is around 1,000 petabytes.
In the metric system, exa is a prefix for 1 quintillion, or 1018. So in some cases, an exabyte is defined as 1 quintillion, or 1,000,000,000,000,000,000 bytes.
But because computers work in binary, computer scientists usually define a petabyte as 1,152,921,504,606,846,976 (10246 or 260) bytes. This works out to 1,024 petabytes.
The abbreviation for exabyte is EB in both the metric system (1,000,000,000,000,000,000 bytes) and the binary system (1,152,921,504,606,846,976 bytes).
Some groups have proposed the name exbibyte for a unit of 1,152,921,504,606,846,976 bytes to prevent confusion. The abbreviation for exbibyte is EiB.