I'm one of them young'uns who wasn't really old enough to understand D&D until Revised 3rd edition. so I've got a few questions...

1. Are AD&D and 2nd edition the same thing? What are the core book(s) to play called?

2. Are OD&D and 1st the same thing? What are the core book(s) to play called?

3. which one of these two had non-human races as classes? both?

4. Are 1st and second edition very dramatically different? like 3rd and 4th were?

5. Can anyone give me a general feel or idea about these systems to help me decide if I'd like them?