A petabyte is a unit of measurement in computers and similar electronic devices that represents a massive amount of data storage capacity. Specifically, a petabyte is equal to 2 to the 50th power of bytes, or 1,000 terabytes (TB). To put this into perspective, a single petabyte of storage could hold 223,101 DVD-quality movies.

Petabytes are used by large organizations to hold massive amounts of data. For example, it is common to see individual companies and even single storage systems with more than a petabyte of storage capacity. Petabyte-level storage is offered by various storage vendors, including Fujitsu, Qnap, Spectra Logic, StoneFly, and Vast Data.

To store a single petabyte of data would take over 170 top-end servers or roughly 61,000 desktops. In terms of memory, a typical laptop or desktop computer contains 16 GB of random access memory (RAM), while a top-end server can contain as much as 6 TB of RAM.

In summary, a petabyte is an extremely large unit of digital data storage capacity that is equivalent to 1,000 terabytes or 2 to the 50th power of bytes. It is used by large organizations to hold massive amounts of data and requires a significant amount of storage space to store.