You will apply this statement when you want to loop data with condition loops.

Example 1: Simple Loop

DATA: lv_int TYPE I VALUE 1.
WHILE lv_int <= 4.
  WRITE:/ lv_int.
  lv_int = lv_int + 1.




ENDWHILE.

The output is 

1
2
3
4

Example 3: Nested Loops

DATA: lv_int TYPE I VALUE 1,
      lv_int2 TYPE I.

WHILE lv_int <= 4.
  WRITE:/ lv_int.
  lv_int2 = 1.
  WHILE lv_int2 <= 2.
    WRITE: lv_int2.
    lv_int2 = lv_int2 + 1.
  ENDWHILE.
  lv_int = lv_int + 1.




ENDWHILE.

The output is 

1  1  2
2  1  2
3  1  2
4  1  2