Oppo Flash File Firmware is the mobile OS officially released & the most stable Stock ROM comes from manufacturers, each device model comes with different stock ROM and Android versions.
Basically, it is an Operating System (OS) that manages & controls all the necessary files, apps & hardware which is required to operate the device, and also provides a simple user interface (UI).
Additionally, you can use it to fix any Software issue, bootloop issue, IMEI issues, upgrade or downgrade OS, Unlock Screen lock, or FRP lock issues.