I was explained Single Responsibility Principle (SRP): A class should have only one reason to change. This means a class should have a single, well-defined responsibility, making it easier to understand, test, and maintain. Open/Closed Principle (OCP): Software entities (classes, modules, functions) should be open for extension, but closed for modification. New functionality can be added without changing existing code, improving stability and flexibility. Liskov Substitution Principle (LSP): Objects of a superclass should be replaceable with objects of its subclasses without affecting the correctness of the program. This ensures that subclasses behave as expected when substituted for their parent class. Interface Segregation Principle (ISP): Clients should not be forced to depend on interfaces they do not use. This promotes creating smaller, more specific interfaces that are tailored to the needs of particular clients, rather than a single large, "fat" interface. Dependency Inversion Principle (DIP): High-level modules should not depend on low-level modules; both should depend on abstractions. Furthermore, abstractions should not depend on details; details should depend on abstractions. This principle encourages the use of abstractions (like interfaces) rather than concrete implementations, leading to more decoupled and flexible systems.