This lecture introduces the concept of operator overloading in C++, focusing on its importance and practical applications. The instructor explains how to overload basic arithmetic operators and the output operator for a class. Examples with complex numbers illustrate the natural and efficient use of operator overloading. Different levels of operator overloading are discussed, from basic arithmetic operators to operators with auto-assignment and return values. The lecture also covers the definition of operators and the distinction between internal and external operator overloading.