A class model represents the model of a Ceylon class that you can instantiate and inspect.

A member class is is declared on classes or interfaces.

This is both a ClassModel and a Member: you can invoke it with an instance value to bind it to that instance and obtain a Class:

shared class Outer(String name){
    shared class Inner(){
        shared String hello => "Hello "+name;
    }
}

void test(){
    MemberClass<Outer,Outer.Inner,[]> memberClass = `Outer.Inner`;
    Class<Outer.Inner,[]> c = memberClass(Outer("Stef"));
    // This will print: Hello Stef
    print(c().hello);
}