The Android recovery mode is a mode of Android used for installing updates and wipe data. It consists of a Linux kernel with ramdisk on a separate partition from the main Android system.
Recovery mode can be useful when a phone is stuck in a bootloop or when it has been infected with malware.
Enablement
The way of entering recovery is different for every vendor.
Examples:
Zebra and symbol devices: left scan/action button
Nexus 7: Volume Up + Volume Down + Power
Samsung Galaxy S3: Volume Up + Home + Power
Motorola Droid X: Home + Power
Samsung Galaxy A10s: Volume Up + Power
Features
Features of the recovery mode usually include:
Applying updates using the Android Debug Bridge
Applying updates from the SD card
Factory
resetting
Mounting partitions
Run system test
Custom recovery
The recovery that is preinstalled on Android can be replaced by other software, such as TWRP or ClockWorkMod. It can include features such as:
Full backup and restore functionality
Applying unsigned update packages
USB mass storage access to SD cards
Full ADB access, with ADB running as root
See also
Bootloader unlocking
Qualcomm EDL mode
References
Android (operating system)