Rooting is basically a process where the access to system level files is given to the third party custom ROM's or the files
so that the required
customization can be made. Only rooting makes it possible to
customize the phone the way we want!
DisAdvantages (Not Root Android)
If rooting process is not
followed properly then you may even brick the device! Rooting voids the Warranty, though can be regained by updating with the default firmware.
Advantages (Root Android)
Rooting allows you to convert the current laggy file system of RFS to the faster EXT4 file system It also allows you to remove the default applications which comes pre-loaded,
It allows you to install the custom firmwares as well as the beta Stock ROMs from different country un officially