The menu contains links to almost all of the actions that you might need to preform on a planet. The menu items are as follows:
Overview: This shows a summary of what is happening on your selected planet such as what is being built or researched as well as some basic stats about the planet. This page also allows you to change your selected planet.
Merchant: The merchant is available on this view. You can trade your own resources for others from merchants.
Research: Allows you to research new technologies.
Shipyard: This page allows you to build spaceships.
Defense: A planet's defenses can be built on this page.
Galaxy: This view allows you to view all the other planets, moons and debris fields and provides information about the owner. You can also find planets that you can colonize on this page.
Recruit Officers: This page allows you to purchase Dark Matter using real world money which can in turn be spent on recruiting officers that allow you to perform special actions that you could not otherwise do.