Procedural coding is about procedures/functions. We write procedures which just take an input and produce an output. They don't have any kind of relation with another procedure. Sometimes they are just able to use some global or shared data when required. OOP is all about objects. We do write procedures/functions in OOP, but the main thing is the class. A class has a relation; it can be a parent or base class, it can be a child class. And then we do things on the objects created by those classes. As classes have relation so we can say that the the objects of those classes do have the relations also. For deeper understanding, you should check for articles online. Just google :)