A Microsoft file hosting and synchronization service.
My team uses software that writes many hundreds of files whilst "building" an output. Once you see the output, you might spot an error and need to rebuild the output a minute later. Since Windows 11 pushes you to put everything under Documents, which is synced to OneDrive by default, naturally the useless OneDrive can't keep up and and the whole thing goes wrong very quickly. Consequently, we have gone back to the 1990s, with all our work arranged inside a C:\WORK folder! We can properly sync/backup that folder at a time of our choosing, using the software of our choice. Everything works nicely, and our backup is fully controllable. OneDrive is nothing but a danger to people's work and creativity.