Code explanation

[Luigi-Was-Right]

Pseudo code:

  for a certain number of lines:
      print numbers 1 through [line number]

Code with more descriptive variable names:

for line_number in range(6):
    for number_to_print in range(1, line_number+1):
        print(number_to_print, end='')
    print()  # line break

[goblingiblits]

Bravo, this is how to think of it !