Depending on what epoch the player is in, they can all sorts of these building. The airport and naval yard is only available in the atomic ages and after ages. Economic buildings produce citizen units, provide resource drop off points, research technologies, or heal units. These buildings basically do not create any units designed to kill the enemy.
Wonders are available to all players and all can be made if the player has enough resources.
They have very useful powers such as seeing enemy buildngs. More details can be found in the Wonder Pages.