Please make sure you have checked the Players Guide thread first, before asking any questions.

Re: Whats the purpose of a MOON?

#2
A moon has a special option called "Sensor Phalanx" (SP). The SP allows you to monitor the activity of nearby fleets. Each level of SP allows the user to see more systems.

Also, a fleet deployed from a moon will be fairly much hidden from other moons within the vicinity.

Moons are notorious for having small field counts. So the SP is usually (and correctly) the only option built on a moon. However, in order to build on a moon, you need to purchase a Lunar Base (LB) to facilitate building slots. Typically, each LB allows you to build three different items. Just make sure that the last item built is another LB.