What Exactly Is Marriage?

"Marriage is when you get to keep your girl and don't have to give her back to her parents" -Eric, six years old
"When somebody's been dating for a while, the boy might propose to the girl. He says to her, 'I'll take you for a whole life, or at least until we have kids and get divorced, but you got to do one particular thing for me.' Then she says yes, but she's wondering what the thing is and whether it's naughty or not. She can't wait to find out."