EFI, the Extensible Firmware Interface, is the firmware layer that initializes hardware before Windows loads. It checks CPU, RAM, storage, and peripherals, then hands control to the operating system.
A few months ago I migrated from an old SSD to a new one. I cloned my Windows 10 partition and have been using it happily since. However, Windows Update is broken ...
This is what you should do if your VirtualBox VM boots only in the UEFI Interactive shell. We talk about Windows and Linux guest OS.