Virtual Destructor in C++

In C++, a virtual destructor is used when a class is derived from a base class. The main purpose of a virtual destructor is to ensure that when an object of a derived class is deleted, all of its resources are properly freed.

A destructor is a special type of function that is automatically called at the end of an object's lifetime. It is used to release the resources utilized by the object. A destructor's name is the same as the class name, preceded by a ~ symbol, like `~ClassName()`.

When we create a derived class from a base class and create an object of the derived class, we must ensure that the derived class's destructor is called correctly upon deletion. If we only use the base class's destructor and do not make it virtual, only the base class's destructor will be called, and the derived class's destructor will not be called. This can lead to memory leaks and other problems.

The example code shows a `Base` class with a virtual destructor and a `Derived` class that inherits from it. An object of the `Derived` class is created using a `Base` class pointer. When this pointer is deleted, because the destructor is virtual, the `Derived` class destructor is called first, followed by the `Base` class destructor, ensuring proper cleanup.