A nested loop is the placement of a loop inside another loop to execute the operations that need multiple loop traversals, such as printing star patterns. Although it helps to make our task easier, it also increases the complexity of the program thus must be used efficiently.

Now, onto the important part: if a loop exists inside the body of another loop, it is called a nested loop. It has no limitations that only similar types of loops can be nested.

We can nest any loop inside any other loop, such as while loop inside for loop, and all different combinations are accepted.

In the chart, first, when we enter the body of the program, a statement such as initialization gets executed. Once a loop is found, the program checks for the condition for the outer loop, and if it returns true, it enters the loop. Once it enters the outer loop and encounters the inner loop, variables are initialized if any are present. Then it checks the condition for the inner loop, and if it returns true, the program enters into the inner loop. This procedure is repeated several times, and then the program exits from the second loop, then the first loop, and move to statements present after the loop.