When all is said and done the best hand at the end usually wins, unless someone has bluffed their way to a win. For people just starting out here are the best winning hands listed from best down.
Royal Flush - From 10 to Ace (10,J,Q,K,A) All cards must be the same suit such as all hearts
Straight Flush - Any five card sequence in order such as 4,5,6,7,8. They must also be of the same suit
Four of a Kind - 4 of the same cards such as all four Kings
Full House - 3 of a kind combined with a pair. If there are 2 full houses then the highest of the 3 of a kinds will win.
Flush - Any 5 cards of the same suit but they do not have to be in a particular order.
Straight - 5 cards in sequence but not of the same suit. example, 5,6,7,8,9 but can be mixed between Hearts, Spades, Diamonds and Clubs
Three of a Kind - any 3 of the same card
Pair - 2 of the same card
If no one has any of the above hands then the winner is determined by the highest card in a hand.