Recovery ROM is firmware for a smartphone installed through the stock Recovery Mode to any HyperOS & MIUI version.

OTA (over-the-air) is the update, containing only changed firmware files. It is installed on the system version specified by the developers, and it's sent to the phone by air.

You don’t need a computer to install the Recovery ROM or OTA. Just download the file with the .zip extension and update the system.

Fastboot ROM is firmware for a device installed in the Fastboot Mode. This mode opens access to advanced settings and allows you to firmware the smartphone.

You cannot perform the OTA Update or Recovery ROM through this mode. Fastboot ROM Firmware brings the device back to life, but it erases all its data.

To install the firmware (the file has the .tgz extension), you will need a computer with a running Mi Flash Pro software.