Years ago, Microsoft took the same algorithm that was being used to generate these things for Remote Procedure Calls in the Open Software Foundation's Distributed Computing Environment and used that algorithm to generate IDs for its Component Object Model. This was all happening in the late 1980s, and at a point where none of it was hard and fast.
If you were doing RPC in OSF DCE your IDs were UUIDs, and if you were doing COM in Wintel your IDs were GUIDs; and that was basically the difference, a different name for the same thing when used in a different domain.
Plus the difference in endianism because one was a network-byte-order network thing and the other was an Intel Architecture byte order thing, and only some parts of these IDs were technically multiple-byte integers with byte orders to have.
But by the late 1990s this had already become lost to history, with a sea of people who had made all sorts of inferences and promoted them as gospel truth, from the fact that Microsoft had two programs named GUIDGEN.EXE and UUIDGEN.EXE, from the fact that many generators sprang up and the whole idea spread to Java and databases and this new-fangled WorldWeb thing and all sorts of stuff, from the fact that there sprang up multiple different versions of these IDs and what version an ID was depended from tooling and libraries, and from the fact that at the time Microsoft was less likely to go through formal standards processes and more likely to just write and ship things and sponsor a book and a CD-ROM of doco so if your world was RFCs and the IETF you had one worldview and if your world was Microsoft Press and the MSDN you had another worldview.
If you were doing RPC in OSF DCE your IDs were UUIDs, and if you were doing COM in Wintel your IDs were GUIDs; and that was basically the difference, a different name for the same thing when used in a different domain.
Plus the difference in endianism because one was a network-byte-order network thing and the other was an Intel Architecture byte order thing, and only some parts of these IDs were technically multiple-byte integers with byte orders to have.
But by the late 1990s this had already become lost to history, with a sea of people who had made all sorts of inferences and promoted them as gospel truth, from the fact that Microsoft had two programs named GUIDGEN.EXE and UUIDGEN.EXE, from the fact that many generators sprang up and the whole idea spread to Java and databases and this new-fangled WorldWeb thing and all sorts of stuff, from the fact that there sprang up multiple different versions of these IDs and what version an ID was depended from tooling and libraries, and from the fact that at the time Microsoft was less likely to go through formal standards processes and more likely to just write and ship things and sponsor a book and a CD-ROM of doco so if your world was RFCs and the IETF you had one worldview and if your world was Microsoft Press and the MSDN you had another worldview.