Some important aspects of earthworm have been reviewed from the time of Aristotle to the present. Many workers have studied earthworm biodiversity, habitat -- relationship, interaction with other biota, life cycle and vermicomposting etc. Aristotle firstly described earthworms as Earth entrails i.e., intestine of earth. Zoological nomenclature of earthworm was given by Carolus Linnaeus. About four thousand species of earthworms have been reported from different parts of the world. Earthworms are hermaphrodite but do cross fertilization. Generally, fertilization takes place in the cocoon outside of the body. Most of earthworm species are plentiful breeders and sustain a high reproduction rate under favorable conditions of temperature, moisture and food availability. Abundance and activities of earthworms are affected by various interdependent physicochemical factors such as soil temperature, moisture, rainfall and food availability. These are considered as important factors to determine the earthworm population. Earthworms have positive interactions with a number of soil biota. Some species of earthworms play an important role in decomposing organic matter and mineral cycling.