It allows you to do something else while waiting for the request to complete. Linux has historically bad hacks to enable this. Windows NT has had IOCP since it's inception, but not only for storage devices, as io_uring is limited to, but networking, TCP sockets, mail slots, named pipes, etc.

"Are you done yet?" vs "Get back to me when you're ready, gonna go do something else". Aka blocking i/o vs nonblocking i/o.

(I always wonder why Windows NT doesn't get more high performance implementations for networking et. al. with this feature; licensing? trade off in perf elsewhere? can't tweak kernel params to your heart's desire?)

io_uring implemented an additional feature of a ring buffer, but Microsoft has followed this feature; I think it was first introduced in a later build of Windows 10 and should be in 11 & 2022.

Microsoft has a graphical example of IOCP:

https://learn.microsoft.com/en-us/windows/win32/fileio/synch...

More info on a comparison of ring implementations in Windows/Linux:

https://windows-internals.com/ioring-vs-io_uring-a-compariso...