Love this one:       A boy is at school and he hears the older kids talking about pussy, and their bitch. The boy confused by this goes to his mother. "Mom", the boy asks, "What's a pussy?"
The mother being startled by this thinks quick and finds the closest dictionary and opens it up to a picture of a cat and says "Son, that is a pussy." the son then asks "What's a bitch?" The mother again thinking quickly opens to a picture of a dog and says "Son, this is a bitch."
The son walks away still confused, and sees his father watching television. The son walks up to his father and says "Dad, what's a pussy?" The father doesn't want to miss the baseball game so he quickly whips out his Penthouse magazine to the centerfold, grabs a marker and draws a circle around the vagina and says "Son, this is a pussy!"
The son, now starting to understand what the older boys are talking about asks "Then, what is a bitch?"
The dad replies, "That's everything outside the circle!"