C# Reflection: Typedefinition.IsNested & Typedefinition.IsNestedFamily

Whats the difference between IsNested and IsNestedFamily ? In the Documentation of Typedefinition I only see IsNested. But according to InteliSense actually there are both Propertys on it.

I can only find IsNestedFamily in the Documentation for the class Type.

So my question:

Can anyone explain to me, the difference between these two Propertys on the Typedefinition class?