I am confused about this video: Doyle Brunson vs Eli Elezra
Why does 555 beat QQQ? Or I am missing something?
Because the 555 are not just 555, it's a full house (fives full of queens). Elezra only has QQQ.
In Hold'em you have to make the best five cards out of seven: using either 0, 1 or 2 of your holecards and either 3, 4 or 5 community cards.
In the deal you linked to the community cards are:
The best hand Eli Elezra can make with his Q⋄2♥ is:
Q♠Q♣Q⋄J♥5♠ (a set of Queens)
while the best hand Doyle Brunson can make with his 5⋄5♣ is:
5♠5⋄5♣Q♠Q♣ (a full house, Fives full of Queens)
Doyle started with 55. Elezra started with Q high. That is to say, Doyle started with the better hand.
The board helped BOTH players. Elezra caught QQ, making trip Queens. Doyle caught a pair of Q's. If this were the end of it, Doyle would have two pair (Qs and 5s), meaning that Elezra would have the better hand.
But Doyle also caught a 5 that further helped his hand, making trip 5s AND a pair of queens, for a full house. This beats "trips."
Put another way, Doyle caught a 5 that made trips (lower than Elezra's), but the two queens improved his hand further to a full house.