The word "homeworld" referred to the planet, the "home planet", or in some cases moon, on which a particular species originated and developed their cultures and their histories on.
For example, Earth was the homeworld of Earth Reptiles, such as Silurians, and humanity. (TV: Doctor Who and the Silurians) In Pete's World, Earth was the homeworld of a race of Cybermen. (TV: Rise of the Cybermen, Doomsday) The Second Doctor referred to Earth as the mother world in relation to the early colonisation of the solar system. (PROSE: The Wheel of Ice)
Skaro was the homeworld of the Thals and Kaleds, later the Daleks. (TV: Genesis of the Daleks)
Gallifrey was the homeworld of the Time Lords, (TV: The Time Warrior) and, due to its important role in the Spiral Politic, it was frequently known as simply "the Homeworld". (PROSE: The Book of the War) Residents of the City of the Saved often called it "the Houseworld". (PROSE: Of the City of the Saved...)
Manussa was the homeworld of the Manussan and Sumaran Empires, both of which collapsed. (TV: Snakedance)
Raxacoricofallapatorius was the home planet of the Raxacoricofallapatorians. (TV: World War Three)