A mebibyte (MiB) is a multiple of the unit byte. It represents a unit of digital information storage used to denote the size of data. It is equivalent to 220,or 1,048,576, bytes.
Techopedia explains Mebibyte (MiB)
Mebibyte was introduced to replace the use of megabyte in computer contextst, where it represents 220conflicting with the International System of Units (IS) definition of the term "mega." In other contexts, megabyte refers to 106 bytes.
Most operating systems use mebibytes to report file and storage sizes. Windows, for example, will report 220 bytes of file as 1 MB while reporting 106 as only 976 kB. The mebibyte prefix was created in December of 1998 by the International Electrotechnical Commission (IEC) to resolve the differences between these common usages.