*face plan* dude. Why would you look up sex on urban dictionary? I think you should ask your parents.....I want nothing to do with ruining your childhood. Now, go ask your mom/dad/guardian about the birds and the bees.
sex is a sensation, driven by temptation. A guy sticks his location into a girl's destination. To increase the population, for the next generation. Do you get my explanation or do you need a demonstration?