Zip Keyword in For loop

[6pathsMadara]

import numpy as np

a = np.array([1, 2])
b = np.array([2, 1])

dot = 0

for e, f in zip(a, b):
    dot = dot + e*f
print(dot)

So after running this the answer is 4, but I don't understand what
the zip keywords functionality is in this loop, in fact I don't understand
any of the loop, can somebody please explain.