There are thousands of uninhabited planets in the universe. These planets just sit there bare until a new player signs up to the game or someone decides to colonise a world. To learn about colonisay read Colonisation..The Galaxy is your Oyster guide . These planets come in all different shapes, sizes and colours as you can see in the picture on the left. They have a various amount of resources ranging from few to great many and you can see these by selecting the planet in the starsystem map. If however you wish to see the resources percentage distribution then you need to fly a probe to the planet.
Many players search for planets that have 2 resources 90% or above and colonise those worlds as there are ten resources and you can have a maximum of five colonies so they focus on 2 resources per planet.