Recursion is a prominent feature of many programming languages and it enables an operation to be described in terms of itself with a halt condition that stops the execution of the code if it is satisfied.

The typical example to demonstrate recursion is the factorial function. This function takes a natural number (N), and returns the product of N and all smaller positive integers.

5! = 5*4*3*2*1 = 120
4! = 4*3*2*1 = 24
3! = 3*2*1 = 6
2! = 2*1 = 2
1! = 1
0! = 1

When a recursive function is called, the computer keeps track of the various instances/states of the function. This is typically done by using a stack. Many operations involving tree data structures also use recursion.

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