How does monotypic genus differ from polytypic genus?

Explanation

Genus: It is a group of closely related species which have evolved from a common ancestor. In some genus there is only one species which is called as monotypic genus Eg: Red Panda
If there are more than one species in the genus it is known as polytypic genus, for example 'cats' come under the Genus Felis, which has a number of closely related species.