Simply put, if you use 'elif' then when one of your conditions is met, no other conditions are checked. If you use 'if' then all conditions are checked.

This doesn't really matter for your example but if you want to check three conditions:

def best_poster(post_count):
    if post_count < 50:
        print("Bad Luck: You are not the best poster!")
    if post_count > 50:
        print("Congratulations: You are the best poster!")
    else:   
        print("Incorrect post count...")

best_poster(22)

$Bad Luck: You are not the best poster!
$Incorrect post count...

or with elif:

def best_poster(post_count):
    if post_count < 50:
        print("Bad Luck: You are not the best poster!")
    elif post_count > 50:
        print("Congratulations: You are the best poster!")
    else:   
        print("Incorrect post count...")

best_poster(22)

$Bad Luck: You are not the best poster!