Catigories of reptiles??

[damzookeeper]

Hi, I will be doing a show for my daughter's class next month. I want to ask the kids a few questions..."What makes lizards different from snakes?", " Reptiles are put into catigories what are the (number) catigories?" I can think of 4, am I right? I think there are 5 but not sure what i'm missing. Turtles and Tortises, Lizards, Snakes, and Crocodilians. Do geckos fall under lizards? Are there anymore that I overlooked? or do amphibians belong with the catigories? Thanks for the help.

Also is there any other interesting questions I could ask the children? They are 10-12 years old. this should be fun. I've only done a few shows before always children under 10 so I kept it pretty simple, but I'd like to ask the kids some questions this time since they have done a project on reptiles in school before hand.
I will have these animals at the show.
a leopard gecko
a fat tail gecko.
a bearded dragon.
a uromastyx.
a box turtle
a wood turtle.
a berber skink
a blue tongue skink
an ocellated skink
a crested gecko
a ball python
a corn snake
a kenyon sand boa
a hognose snake
a giant african land snail (just for fun)