Wonders: Armada is an expansion for 7 Wonders that can be combined with the base game or any combination of expansions.
With this expansion, each player gets a separate "naval" board at the start of the game in addition to their wonder board. The expansion includes additional red, green, yellow, and blue cards to shuffle into the deck, and each time that you pay for the cost for any red, green, yellow, and blue card — not only the ones added in this expansion — you can pay an additional cost shown on your naval board to advance your ship of the matching color. When you advance the red ship, for example, you gain naval strength, and at the end of an era, you compare your naval strength against all the players at the table, not only adjacent players, to determine who's strongest, who's second-strongest, etc., with victory points handed out accordingly.
Advancing on the yellow and blue tracks gives you coins and victory points, respectively, with additional naval strength at the far end of the tracks. Advancing on the green track allows you to discover islands, and to do this, you draw the island deck of whatever level you reached, then choose one of the islands in that deck and put it into play. Maybe you'll increase your navy, advance a ship of another color, find a source of raw materials...you'll see when the time comes!