This question popped into my head when I learned some Citation X series have shared (?) type ratings.
So a theoretical situation:
I am a happy person with PPL and IFR ratings and then I decide to rent a 737-800 to give a birthday party to a close friend.
Can I just charter a private jet (assuming I am lucky enough to find a company that will give one to me) and fly? Do civilians need type ratings? I have heard you need a type rating to be the pilot in command. (It wouldn't be hard to find a pilot if that is the case.)