There are event you can predict on that even though it's not 💯 guaranteed that you're going to win, a level of certainty makes you think that you're surely going to win.
Like PSG vs Chelsea and then they went ahead losing to Chelsea 
, there's no guarantee about a future event , it's just what you believe would happen, doesn't mean another person won't see it differently no matter the level of certainty or whatever you think and lo you could be wrong as well .. that's why it's called gambling