What are the various ways an android phone can be locked? I ask this question because the confusing terminology of different types of &quot;locked&quot; and &quot;unlocked&quot; like rooted and not rooted, Sim-locking, FRP locks, lock screens, adb active debugging, and black listed phones, and even carrier locking. These are very confusing.
Can someone disambiguate this for me?
Rooting is the process to modify core OS components so that apps/processes can be run with high privileges (UID 0).
See details in How Magisk works? and How to manually root a phone?
Rooting is not itself locked or unlocked. But Unlocking Bootloader is usually a prerequisite. Bootloaders are the initial components which load on device boot. OEMs lock them so that to restrict any deliberate or malicious changes to core OS components.
See Is there a way to root an Android phone without unlocking the bootloader?
Initially it was possible to unlock bootloaders just by issuing one or more fastboot - Android's standard protocol to communicate with bootloader - (or equivalent) commands. However now many OEMs, including Google, add an extra layer over bootloader unlocking called OEM Unlock. It's a toggle switch in Developer Options (in Settings app) which is a prerequisite to bootloader unlocking. That is, a thief won't be able to unlock the bootloader and refresh the device to completely new state (e.g. by clearing FRP, see details below) until the screen lock is active.
Also some OEMs may require the user to get approval from OEM before bootloader unlocking, others may provide no option to unlock bootloader at all.
Screen Lock backed by a password or PIN or biometrics is the one we are all familiar with. It restricts unauthorized use of (at least many of) device features. On older devices this was only software-based. New devices provide hardware backends (like TEE and SE) to store credentials more securely.
Factory Reset Protection ties the Google (and/or OEM) account to the device. This info is saved to a secure place (usually a tiny partition) on the device and cannot be erased by doing factory reset, flashing ROM or flashing Factory Firmware. After Factory Reset user is asked to enter the previously entered account's credentials. So FRP is more focused on anti-theft protection. Some OEMs disable FRP when OEM Unlocking is enabled (but it doesn't matter when bootloader is unlocked).
Also some OEMs now go even beyond that, and they'd ask lockscreen or account credentials before performing Factory Reset.
SIM Lock can be either SIM Card Lock or another term for Carrier Lock. Former is independent of Android or the device it's being used in. SIMs are Secure Element chips i.e. they have their own processor and OS. You can set a PIN lock on SIM to restrict any unauthorized use.
Carrier Lock or Network Lock binds a phone (or some other device) to a carrier i.e. a service provider. This bond is usually a part of device purchase agreement, and may end after a fixed time period. There also exist ways to do Carrier Unlock, which may not be legitimate.
See How does carrier/network lock work? How is it implemented?.
Not sure in which context you are referring the term black listed phones. IMEI blacklisted? IMEI is device's unique ID which the carriers may use to block a device from using their services after the device is reported lost or stolen or involved in some misconduct. IMEI/ESN blacklisted phones might or might not be unlockable depending on the reason of locking, the carrier's policy, and the availability of unlocking hacks.
See this answer for some details on device identifiers.
ADB Debugging is Android's standard way to let ROM and app developers communicate with Android device from a PC over USB or Wi-Fi connection. End users may also use ADB shell (like any other UNIX shell) to issue commands. ADB has no direct relation with any (un)locking mechanism.