What exactly is the paidia form and ludus form?

Hey guys i was wondering if any of yous can help me. I study Games Design and i had a lecture about play in games which included theories of French Sociologist Roger Caillois but unfortunately i didnt attend to that lecture since i was ill. He also explains about the paidia form and the ludus form and i have ignment to hand in about the two forms and its the holiday now and is too late to ask my lecturer. I've read books and read online but i didnt quite exactly understand it so in simple terms could anyone tell me exactly what is the paidia form and the ludus form and if possible give me the sources, that will be much appreciated