Building Types
Tapping at either the "special" button on the top left when viewing the upgrade screen, or from the Options screen will lead to this section. Special buildings are unique buildings that you unlock. They generate way more money than regular buildings. You can only have one of them in a current City and they are automatically marked as Historical so they aren't overwritten.
special Buildings aren't recommended unless you have purchased the other more meaningful upgrades with your bux.
Regular
Regular are the buildings you see normally without spending bux. Most of your buildings will consist of these. They have nothing special attached to them except aesthetically.
Unlocked & Locked
Locked is where you go to purchase the "locked" special buildings and see their cost, design, and effects.
The Unlocked section is where you can see which special buildings you have purchased.
Residential, Services, & Business
These types have no large effect on the game. The only time they will have an effect is if they meddle with the Demand and if you are doing a task that needs a particular Building type like having 5 corn fields in your City which are large service lots.