1. To understand recursion, you must first understand stacks.
2. In a stack data structure, you can only add and remove from the top of the stack.
3. The term for adding to a stack is pushing, while removing from a stack is popping.
4. Python lists can be used as a stack, with the append() method for pushing and pop() method for popping.
5. Function calls make use of a stack called the call stack.
6. The call stack pushes frame objects when functions are called and pops them when functions return.
7. Frame objects contain the local variables and return address for a function call.
8. The sys.setrecursionlimit() function can change the maximum recursion depth. The times that it’s appropriate to call this is never.
9. Recursive functions must always have at least one base case and at least one recursive case.
10. "Iterative" means the code uses a loop.
11. Unlike recursive algorithms, iterative algorithms will never stack overflow.
12. Recursion and iteration are equally powerful. There is nothing recursion can do that you can't do with a loop and a stack.
13. The recursive factorial solution can be confusing because code is run both before and after the recursive call.
14. The recursive factorial solution isn’t used in real world code because calculating large factorials results in a stack overflow.
15. The recursive Fibonacci solution isn’t used in real world code because calculating large Fibonacci numbers requires like trillions of years.
16. Recursion is a good technique to use when the problem involves tree-like data structures and back-tracking.