Planets with gravities between 0.4 and 2.5 can be terraformed to a habitable 72 F. Aliens may have other preferred planetary conditions. Money for terraforming activities ALSO comes from income derived from previously terraformed worlds. When one of your ships lands on an unexplored planet, you get visual and auditory feedback about its suitability as a potential colony. Landing on planets held by enemies initiates combat. Landing a scout or fighter on a planet does not create a new colony.
Colonization is achieved by landing a colony ship.
Aside from the fact that colonization can lead to profitable planets in the fullness time, any ships you have on a colonized planet will automatically refuel within one turn and can then be sent on to visit other planets that are in range. Colony ships should be treated with respect, since they are relatively expensive, and use more metal than fighters or scouts. The window below that indicates information about a fighter that has landed on Bambi. Below that are several windows. Another window say how much metal, ships savings, and net income I have.