Poker hands from highest to lowest:

Royal Flush
A, K, Q, J, 10 of all the same suit

Straight Flush
Five cards in a sequence, all in the same suit

Four of a Kind
All four cards of the same rank

Full House
Three of a kind, with a pair

Flush
Any five cards of the same suit, but not in sequence

Straight
Five cards in a sequence, but not of the same suit

Three of a Kind
Three cards of the same rank

Two Pair
Two different pairs

One Pair
Two cards of the same rank

High Card
When you haven't made any of the hands above, the highest card plays.
In the example below, the jack plays as the highest card.