These add +1 economy to your base. Also uses your base metal deposit to lower production time.
Robotic Factories
Lowers production time by a factor of 2. They are found on beginning planets. Its big brother is the Nanite Factory.
Android Factory
This lowers production time by a factor of 6. Its the largest factory and is quite useful when going into a production frenzy.
Capital
Be careful with this structure. It boosts your economy by giving it +10. You are only allowed to use it once, and the biggest problem you'll face is that it will be a prime target by levi drops. Make sure that the base this is located on is a Fortress.
Orbital Shipyards
Allows you to build only the largest ships. It can allow you to build anything bigger than a dreadnought.
Crystal Mines
Can only be used on planets with crystal resource. Its advised to only use it when you have a crystal deposit of 2. Best used on : Asteroids, Crystalline
Nanite Factory
Lowers production by a factor of 4. This also adds +2 to your economy. Its big brother the Android Factory.
Economic Center
This boosts your economy by giving it +3 economy per level on a base.
Shipyard
This structure allows you to build ships for your fleet. The more shipyards you have the more types of ships. Whenever you see this num(x) it refers to amount of Orbital Shipyards required.