Source: Engadget
While OneDrive on Windows has been around since 2007 and the first 64-bit version of Windows came out in the early aughts, now is just the first time the OneDrive app on Windows will get a 64-bit version. This version comes out in a new client preview. This means for those with 64-bit machines, you'll be able to quickly transfer large files since it can access more resources than the 32-bit option.
The preview is currently limited to the x64 installs of Windows. Those who have Windows 10 on ARM might have to wait a bit. In the meantime, use the 32-bit version of the app.
Source: Engadget