7 Wonders lasts three ages. In each age, players receive seven cards from a particular deck, choose one of those cards, then pass the remainder to an adjacent player. Players reveal their cards simultaneously, paying resources if needed or collecting resources or interacting with other players in various ways. Each player then chooses another card from the deck they were passed, and the process repeats until players have six cards in play from that age. After three ages, the game ends.
In essence 7 Wonders is a card development game. Some cards have immediate effects, while others provide bonuses or upgrades later in the game. Some cards provide discounts on future purchases. Some provide military strength to overpower your neighbors and others give nothing but victory points.
Though the box is listed as being for 3-7 players, there is an official 2-player variant included in the instructions.