A GUID (globally unique identifier) is an arbitrary 128-bit identifier. It is the Microsoft version of UUID.
When written in standard text form, a GUID looks something like this:
In binary form, the first three fields are supposed to be stored using native endianness. Since Microsoft platforms usually use little-endian byte order, the above GUID would typically be stored as the following 16 bytes:
03 02 01 00 05 04 07 06 08 09 0a 0b 0c 0d 0e 0f