The “Program to Interfaces, Not Implementations” principle is- Design your code to depend on interfaces, and avoid the dependency on concrete classes. The process is to define interfaces that specify required behavior. Classes then implement the interface and allow the system to extend and modify the implementation, without changing the dependent code.
The Composition Over Inheritance(COI) principle is- We should prefer composing objects while creating a complex object, rather than relying on inheritance. This means, whenever possible we should avoid hierarchies of class inheritance, and compose objects of a class when we need it.
This Encapsulate What Varies(EWV) principle is- Isolate the part of the code that is likely to be changed later, by encapsulating them. So that the encapsulation works as a shield for the rest of the code.