Nearby Share in Windows 10 allows transferring files between files within the same network. It is a great and somewhat underrated feature that will let you ditch third-party sharing apps and slow USB thumb drives. Being integrated into the OS, Nearby Share ensures the best compatibility with almost any Windows 10 device.
I would add that it is pretty much unknown, even by a geek like me.
You need relatively recent version of Windows 10, e.g. 1803 or later. You also need Bluetooth enabled and having the 2 PCs on the same Wi-Fi network increases the speed of transfer.
To use Nearby Share, on both systems go to Settings > System > Shared Experiences and turn on Nearby Sharing.
To share a file, right click on a file in Windows Explorer and chose "Share".
You'll get this notification on the sending system.