Odin3 is a free PC application which can flash and root Android-based phones.
With Odin3, you can flash your Samsung cell phone and overwrite the system files. You can install any version of the Android OS on your smartphone before your phone manufacturer has released an update, putting you on the bleeding edge of software. Once your phone has been rooted, you are able to do all sorts of things.
Odin3 makes a phone rootable by installing a custom kernel giving you permanent root access. Users are however cautioned because installing custom operating systems or kernels can brick your device.