Those lines are actually related to preventing the compiler from generating default copy constructor and copy assignment operator for the D3DApp class. By using = delete, you're essentially telling the compiler not to allow copying of D3DApp objects. This is often done to prevent unintended behavior or resource management issues, especially in classes that manage resources like memory or handles. So, in essence, those lines ensure that instances of D3DApp cannot be copied or assigned to another instance, helping to maintain the integrity of the class's design.