Use of Else outside an if

Question

I was writing a program that would give me all prime numbers between 1 and a certain number that should be informed by the user. After several adjustments to the code, I came to the following final version, which apparently works as it should:

from math import *
num = int(input("Informe o limite dos primos: "))
for i in range(1, num+1):
    for j in range(2, ceil(sqrt(i+1))):
        if i % j == 0:
            break
    else:
        print(i, end = " ")

The code provides the following output:

================ RESTART: C:\Users\usuario2\Desktop\Primos.py ================
Informe o limite dos primos: 20
1 2 3 5 7 11 13 17 19 
>>> 
================ RESTART: C:\Users\usuario2\Desktop\Primos.py ================
Informe o limite dos primos: 50
1 2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 
>>> 
================ RESTART: C:\Users\usuario2\Desktop\Primos.py ================
Informe o limite dos primos: 100
1 2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97 

However I noticed something very curious: I have one else out of a if. How can it? in my view, it should not work. Why does it work?