All Giffen goods are inferior goods. But not all inferior goods are Giffen goods.

For inferior goods, the negative substitution effect will more than offset the positive income effect, so that total price effect will be negative. For Giffen goods, the positive income is positive and very strong that the law of demand does not hold. Price elasticity of Giffen good is positive.

Inferior Goods: Cheap goods

Giffen Goods: Rice, wheat, noodles are Giffen goods in China

The phrase "All Giffen goods are inferior goods, but not all inferior goods are Giffen goods" implies that a company called Giffen only creates goods that would be deemed inferior. By contrast, however, it cannot be assumed that any inferior good has been produced by the Giffen company.

has a positive income effect

is an nferior good

Robert Giffen was born in 1837.

Walter Giffen was born in 1861.