Four of a kind in poker is exactly what it sounds like, having 4 cards of the same kind! When it is said in this manner it doesn’t sound like it would be too hard to achieve, but in fact 4 of a kind is so rare that some casinos and Online Poker Sites even have bad beat prizes when you lose with them, and jackpots when you make them! Your odds of hitting 4 of a kind on the flop is a massive 1 in 4100. Even if you increase that to seeing all 5 cards you are still looking at seeing 4 of a kind around once every 2000 or so times!
Just like always there are rules for which 4 of a kind beats which, and again it is the highest 4 of a kind that will win out. If in the extremely rare instance that both players have the same 4 of a kind (meaning all 4 of the same card came down on the board) then the highest kicker will play. One interesting fact about getting a 4 of a kind is that you generally want to get make a lower 4 of a kind rather than a higher one. This may seem counter intuitive but when you think about it for a few moments it starts to make sense.
If you were dealt pocket Aces and the flop came down something like A A Q then it is very unlikely that many people will call more than one bet as it is quite likely you would have at least one Ace in your hand while they have none. If however that flop was 2 2 Q and you now had quad 2’s, well not many people would think you have a 2 and would guess that you are betting with a Queen so now you can build a big pot against an opponent without as much fear of them folding! With the odds of making 4 of a kind as high as a few thousand to one, the odds of making 4 of a kind and then losing to a bigger 4 of a kind is so astronomical that most people will play poker for their entire lives and never see it happen.
This is why certain Online Poker sites have bad beat jackpots, where if you lose in a situation like this you win a jackpot of some kind. This typically eases the blow of the loss and instead just leaves the player with a funny story to tell. Typically the smaller the site the more likely they are to have this bad beat jackpot as they won’t have to pay it out so often! There isn’t really too much else to say about 4 of a kind really. When you make the hand there is such a small chance of losing the hand that it’s not even worth thinking about and we’d simply say get as much money into the pot as you possibly can!