Public methods are functions defined within a class that can be accessed from outside the class. They allow other parts of a program to interact with the class's data and behavior. For example, if a class represents a Car, a public method might be used to start the engine or display the car's current speed. These methods are essential for encapsulation, a key principle in object-oriented programming. By using public methods, developers can control how data is accessed and modified, ensuring that the internal state of an object remains consistent and secure while still providing necessary functionality to users.