In poker, hands are ranked based on the rarity and strength of the combinations players can form. The hierarchy starts with the high card, followed by one pair, two pairs, three of a kind, straight, flush, full house, four of a kind, straight flush, and the rarest, the royal flush. Understanding these rankings is crucial for strategic play, as they determine the winner in a showdown. Mastering hand rankings not only enhances gameplay but also sharpens decision-making skills, making it an essential aspect of poker strategy.