When a class is derived from single base class and derived class can’t work as base class for another class called single level inheritance.
Example:

class A{

    public:

       void show(){

                  cout<<"show\n";

       }

};

class B: public A     // example of simple inhieritence

{

       public:

            void display(){

                        cout<<"display\n";

            }

};

void main(){

            B obj;

            obj.display();

            obj.show();

}