SC2Mapster

Buildings help to boost colonies developments.
This is why you should focus development on one thing per colony as workers% effects buildings efficiency.

Economy buildings: boost mineral income.
Production buildings: decreases ship building time.
Research buildings: increases science stat growth and decreases research time.
Administration buildings: allows you to have more colonies.
Mines: increases mining.
Habitability buildings: increases the planet habitability, however you cant have more than 100% habitability on a planet.