The concept of inheritance is a basic object-oriented development concept. Inheritance allows a class to be defined as having a certain set of characteristics and then other classes can be derived from that class. The derived class inherits all of the features of the class it is inheriting from (unless the derived class overrides those characteristics) and then usually adds additional characteristics of its own.
With inheritance, we can create what is known as a class hierarchy. In a class hierarchy, the class at the top of the hierarchy is known as the base class and the derived classes are known as subclasses. We are not limited to only creating subclasses from a base class, we can also create subclasses from other subclasses. The class that a subclass is derived from is known as the parent or superclass. In Swift, a class can have only one parent class. This is known as single inheritance.