The exercise-rep counter
A coach says 'do a push-up for each number up to ten' — you repeat one action, counting as you go. A Python for-loop is that counter, and a while-loop is 'keep going until you're too tired,' repeating until a condition changes.
for and while
for i in range(3):
print(i) # 0, 1, 2 range(n) stops before n
range(3) gives 0, 1, 2 — exactly three values.