In this classic word game, players use their seven drawn letter-tiles to form words on the gameboard. Each word laid out earns points based on the commonality of the letters used, with certain board spaces giving bonuses. But a word can only be played if it uses at least one already-played tile or adds to an already-played word. This leads to slightly tactical play, as potential words are rejected because they would give an opponent too much access to the better bonus spaces.
Don't just take our word for it! Check out this review of Scrabble.