You are telling your computer you want to reboot your computer and then boot into Windows unattended (you can walk away and unless Windows crashes itself, it might be running).
You have to interrupt the boot process to make a selection in grub, the one-liner above makes that one-time selection for you in advance. So you can walk away and get a coffee while your computer does the OS switch.
Excuse my ignorance, but what’s the difference between this and GRUB?
You are telling your computer you want to reboot your computer and then boot into Windows unattended (you can walk away and unless Windows crashes itself, it might be running).
You have to interrupt the boot process to make a selection in grub, the one-liner above makes that one-time selection for you in advance. So you can walk away and get a coffee while your computer does the OS switch.