In Java, the keyword "extend" is used to create a relationship between two classes where one class inherits the properties and methods of another class. When a class extends another class, it becomes a subclass, and the extended class becomes its superclass.
Inheritance is the process by which one class acquires the properties and behaviors of another class. It allows for code reuse and promotes hierarchical organization in object-oriented programming.
A subclass is a derived or child class that extends or inherits from a superclass. It inherits all non-private members (fields and methods) of its superclass while also having its own unique members.