From the game guide

Content Editors

The editors are the heart of Spore. They allows players to create content through a graphical interface. You can modify your creature, construct buildings, or make new vehicles for your creatures. The premise of the editors are to give players simple shapes - and let them modify it to create whatever they want.

The basics of the editor are very easy to use and well thought out. Will has had the luck of experimenting with all kinds of content creation tools ranging from Sim City 2000 to The Sims series. The editors in Spore will allow you to create any type of animal or building you can conjure up in your imagination.

There will be many editors to accompany each of the five gameplay stages.