Resource planets generate resources. Resources are used to create planets, ship streams and upgrade your planets.
You can't create resource planets, just generic planets, so make sure you start near them or you own them.
As you might have noticed they cluster in the center of the game where is harder to keep them under your domination.
In the top right part of your screen you can see how many resources you have. In this case 31.
This is a resource planet:
To see how many resources a planet generates, select the planet and click on upgrades:
Then scroll down to "Resources per cycle":
Here says that is creating 1 resource per cycle. A cycle happens every certain amount of time. Click on the blue part where says "Upgrade" to generate more resources per cycle.
Originally published December 14, 2018, updated December 14, 2018