Goose breeds are usually grouped into 3 weight classes: Heavy, Medium and Light. Most domestic geese are descended from the Greylag Goose (Anser anser). The Chinese and African Geese are the domestic breeds of the Swan Goose (A. cygnoides); they can be recognized by their prominent bill knob.
Some breeds, like the Obroshin Goose and Steinbach Fighting Goose, originated in hybrids between these species (the hybrid males are usually fertile – see Haldane's Rule). In addition, teo goose species are kept as domestic animals in some locations, but are not completely domesticated yet and no distinct breeds have been developed.
A small flock of Pilgrim Geese - an example of color-sexing goose; males are white, females are gray
The plumage of male and female goose is usually the same. However, there are few auto-sexing goose, which are sexually dimorphic and the gender can be recognized on the first look by plumage. In general, ganders are white and females are either entirely gray, or pied gray and white.