ADB and Fastboot are two tools that allow you to communicate with Android devices from your computer. ADB stands for Android Debug Bridge, and it lets you perform various actions on your device, such as installing apps, transferring files, or debugging. Fastboot is a mode that lets you flash firmware, boot images, or recovery images to your device. You can use ADB and Fastboot to unlock the bootloader, root your device, or install custom ROMs.