White Hat Hacking

I do not know anything about this topic that is why I chose it.

What is the difference between it and normal hacking?
Is it special, is it specialized in hacking some sort of code, program or page?

http://www.investopedia.com/financial-edge/0811/famous-white-hat-hackers.aspx#axzz27fo7GNof
http://www.secpoint.com/What-is-a-White-Hat.html

• white hat hackers are the good hackers to put it in a way, use their hacker abilities for good
• they help out organizations that might have security breaches, and they let them know of this breaches so that they can fix it and avoid getting hack
• they are ethical hackers 
• they are also known as white knights, sneakers, white hats or as we already know white hat hackers
• they are the opposites of the black hat hackers
• the NSA offers certifications to this type of hackers 
• they literally hack into a system of software of a company from many points so search or spot any weaknesses 
• Then after they spot them they go ahead and fix or close the breach they found,m and strengthen the security system of that company or software

well it relates to my life in a way that i like to see or discover new ways to hack into my own Facebook account so that when somebody seriously does it to me i can counter-hack it and know exactly what to do.
i also like to do this when my friends get hacked and help them take action. By the way I also like hacking for personal purposes but not to hurt any software or page. I would also like to do this to help companies avoid getting hacked by black hat hackers.

What is a grey hat hacker?