Difference between ADB drivers and MTK drivers?
Firstly it's not ABD driver it's Adb driver.Adb means Android Debug Bridge.ADB is a command-line utility included with Google's Android SDK. ADB can control your device over USB from a computer, copy files back and forth, install and uninstall apps, run shell commands, and more.When your device is in Fastboot/Download mode you can access your phone only through Adb.
For example if something goes wrong while flashing a rom and your phone is softbricked.Only way to access a bricked phone is through Adb.Adb mainly not used for flashing rom, It's used for flashing recovery/bootloader.