The Gamma 4 Build/Launch Facility is used to build and launch the Gamma 4 rockets you will need later in the game to terraform Mars.

Gamma 4 rockets can also be built in the ShipYard, but you may want to keep those free to build the terraforming modules, such as the Mars Aeroponic Module to send on these Gamma 4 rockets. If you build Gamma 4 rockets in your Shipyard, you then launch them from a 1x1 Landing Pads.

The advantage of using the Gamma 4 Build/Launch Facility is that you have a build and launch facility all in one, rather that using a ShipYard that could be building terraforming modules as well as needing a 1x1 Landing Pad.

MoonBase Inc Mars rockets