Difference between 2*3 and 3*2

Boy: "I got an F in Arithmetic"

Dad: "Why ?"

Boy: "The Teacher asked 'How much is 2 * 3 ?' and I said it is '6' "

Dad: "But that's right only na.."

Boy: "Then she asked me 'How much is 3 * 2 ?' "

Dad: "What's the XXXXX difference ?"

Boy: "That's exactly what I said!"