Mother goddess is a term used to refer to a goddess

Goddess

A goddess is a female deity. In some cultures goddesses are associated with Earth, motherhood, love, and the household. In other cultures, goddesses also rule over war, death, and destruction as well as healing....

 who represents motherhood, fertility

Fertility

Fertility is the natural capability of producing offsprings. As a measure, "fertility rate" is the number of children born per couple, person or population. Fertility differs from fecundity, which is defined as the potential for reproduction...

, creation or embodies the bounty of the Earth

Earth

Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

. When equated with the Earth or the natural world such goddesses are sometimes referred to as Mother Earth or as the Earth Mother.

Many different goddesses have represented motherhood in one way or another, and some have been associated with the birth of humanity as a whole.