Welcome to the forums. I moved your question to the appropriate forum where you'll get better answers.
The short answer is rooting is gaining administrative access to the file system which allows you to modify the device beyond the stock features or options. The benefit of rooting is only evident if you want to do something that requires root privileges. And, it is not without risk, for example, if you accidentally move or delete a system file.
The process to root depends on which version of Android you have on your phone. Go to settings>about phone and look for Android Version. And you can unroot, but the process also depends on how you rooted in the first place.