Loops are a way for your program to repeat something.
For example, if you wanted to show the numbers from 1 to 999 it would be very tedious to write 999 separate lines of cout <<
However, we could easily write a loop that would do this using 2 lines of code:

for (int i = 0; i<1000; i++)
cout << i << endl

In the above example the loop :

starts variable i at 0 (int i = 0),
stops when i is no longer less than 1000 (i<1000)
increases i by 1 (i++) every time
shows the numbers 1 through 999, one per line

Types of Loops:

There are two types of loops: for, and while.
The for loop is a shorter version of the while loop.
One can always use a while loop instead of a for loop.
However, it is shorter and easier to use a for loop when you know how many times the loop needs to happen.
The while loop can be used as an IF that happens multiple times. A while loop can go on forever until the user stops it.

REPETITION: FOR Loop, WHILE Loop, DO-WHILE Loop: