The ranks are (from highest to lowest)

Royal Flush - A, K, Q, J,10 all the same suit
Straight Flush - Five cards in a sequence, all the same suit
Four of a Kind - All 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 a 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

Pair - Two cards of the same rank
High Card - When you haven't made any of the hands above, the highest card is played