What is "root"?
Basically, root is the user with the id
0, the "first citizen", the only one with full permissions to everything on the OS level of Unix/Linux systems. Hence, it is the "Administrative Account" -- which on the named Unix/Linux systems is acessible by default (even if not always directly).
Android bases on Linux (it runs on top of a Linux kernel). But as the devices ship, their "root" accounts are usually not accessible (to save the manufacturers/services from the requests of "noobs" having used the root-powers inadequatly and broken their system, e.g. by uninstalling core apps). The process of gaining root access to your device is called rooting.
So what is this tag about, when should I use it?
This tag is not intended to show-off: "Hey, I've got root on my device!" -- but rather to indicate "My issue is connected with root". You need not specify it when other tags already make this clear: e.g. link2sd would imply root, as the Link2SD app does not work without root access. Same applies for titanium-backup, and most likely several other tags.
- rooting: for questions about how to get your device rooted
- unrooting: for questions on reverting the 'rooting' process (which might be neccessary e.g. if you need to turn in your device to a repair-service)
- superuser: an app to manage which other apps will be granted root permissions. An alternative is the SuperSU app.
Further readings on this site
- I've rooted my phone. Now what? What do I gain from rooting?
- How can I tell if I have root?
- Do all applications run as root on my phone after rooting?
- How do I protect my phone from malicious apps once it is rooted?
- How can I execute command in the terminal as root?
- Root and OTA-Updates (list of related questions)
- Why do phones have default limited user rights (not rooted)?