From Academic Kids
Terrestrial literally means 'of the earth' and is used in a variety of contexts:
- In biology and in the general sense, terrestrial means indicates ground-dwelling (compare aquatic). See land.
- In broadcasting terrestrial indicates that TV or radio signals are received through a conventional aerial. See terrestrial television.
- In communication networking, "terrestrial" indicates signals travelling through fiber optic cable or copper wire, usually located underground or undersea.
- In astronomy, terrestrial can refer to the first four planets (http://en.wikipedia.org/wiki/Planet) in the solar system - planets with a rocky exterior.
- Terrestrial may also be used in contrast to extra-terrestrial, indicating anything of Earth-origin rather than from outer space.