A Terrestrial Planet is any silicate (rocky) planet orbiting a star. They all have a central metallic core, silicate mantel around that and a thin crust is a planet's surface. These planets are usually smaller than a gas giant. A planet with volcanic activity has liquid magma underneath the crust.
An Earth-like World is a terrestrial planet with life-supporting characteristics similar to Earth. All Earth-like Worlds, either naturally-occurring or terraformed, support a wide variety of plant and animal life. Other indigenous lifeforms may be encountered on other types of terrestrial planets, such as Ammonia Worlds.
- The word "terrestrial" comes from Latin terrestris meaning "earthly."