Object Oriented Programming (OOP for short) is a programming paradigm that brings significant simplification of development work.
The main advantages of OOP are the division of code into individual parts (objects and methods) that can be easily transferred between projects (abstraction and encapsulation) to build reusable applications. OOP also introduces new techniques such as inheritance and polymorphism for the first time.
This entire section of the site describes the benefits of OOP development in an extensive way. You will soon discover that although OOP has its problems too, it is actually the best methodology to build something if you care about code reusability and long-term support for applications you have already written.