Default [Q] Rooting sm p601

I am new Samsung mobiles and I want to Know what is rooting , and how could it affects my experience with the tablet. Is it illegal? Can any one link me to a detailed explanation and benefits for rooting + detailed Steps on how to root ? Can this give me latest Software updates before its release ? would this decrease S-pen functionality ? Sorry for all that but I feel very Losted.

Another question , I have no carrier for my tablet does this prevent me From getting updates.