Actually machan.. it goes like this...
JAILBREAKING is something illegal... Normally, there are limitations in iPhones, to unlock them, people break the locks but according to the law, its illegal! Apple don't like it!
ROOTING means, you are installing a new OS in your phone... Think of an android phone as your computer... It comes with an OS installed by the vendor by default... But, when you buy the phone, you owns it and you can do anything with it... Android don't limit you! So, if you want, you can format the phone and install a new OS...
There are lot of custom Android build you can use on your phone. They are not illegal... Android is open source... any one can take the source code and build their own version... If you really want to root, try Cyanogenmod :
http://www.cyanogenmod.com/ or MIUI :
http://en.miui.com/
I don't know about MIUI but I have already rooted my Android phone with Cynogenmod. And another thing... Cyanogenmod's main developer is a senior developer at Samsung
But, Warning... Some hardware vendors like HTC don't like rooting.... Actually, they are right... If we break our phone trying to put a third-party OS, they can't take the blame.. So, if you root the phone, you'll loose your WARRENTY!
Reasons for rooting :
1) To install a newer version of android (Normally, these custom mods have never versions of Android. But I think Samsung have given the latest Android 4.0 to S II. I don't think the custom ROMs have it yet...)
2) Android developers do this in order to build software for the device!
If you are not a Linux user and don't know anything about it, stop reading from here... If you are one, keep reading....
Android is a Linux OS. Built on Linux! Actually, rooting is not exactly installing a new OS. If we root a device, then we can get administrative privileges to the phone. Otherwise we only have normal user privileges... With those privileges, we can't install a new OS or do some serious geeky stuff with the phone.. So, people root the device!
