Question

what is nested loop

Answer 1

Nested loop is a loop inside another loop.

Answer 2

a loop within loop is called nested loop.
it can be applied when the internal loop repeats for a given no. of times for each iteration of external loop.
 
loop1(cond.1)
{ --------
----------
loop 2(cond. 2)
{---------- 
-----------
loop 3(cond.3)
{-----------
-------------
}
}}