Primitive recursion

Primitive recursion is a method for defining functions where the value of the function for a larger input is built from simpler cases. It starts with a basic base case (like the value when input is zero) and then defines the function for bigger inputs using the previous value. Think of it as climbing a staircase: you know the first step, and each subsequent step depends on the one before. This approach helps create complex functions from simple, well-understood steps, ensuring they are computable and well-defined within mathematical systems.