In OOPS we mainly concentrate on Objects.
Every object has got two things: Member Data
And Member Methods.
OOPS concept revolves around mainly on 4 things those are Abstraction, Encapsulation, Inheritance & Polymorphism
An object type is a user-defined composite datatype that encapsulates a data structure along with the functions and procedures needed to manipulate the data. The variables that form the data structure are called attributes (MEMBER DATA). The functions and procedures that characterize the behavior of the object type are called methods (MEMBER METHODS).
We usually think of an object (such as a person, car, or bank account) as having attributes and behaviors. For example, a baby has the attributes gender, age, and weight, and the behaviors eat, drink, and sleep. Object types let you maintain this perspective when you sit down to write an application.
Object types reduce complexity by breaking down a large system into logical entities. This allows you to create software components that are modular, maintainable, and REUSABLE. It also allows different teams of programmers to develop software components concurrently.
By ENCAPSULATING operations with data, object types let you move data-maintenance code out of SQL scripts and PL/SQL blocks into methods. Object types minimize side effects by allowing access to data only through approved operations. Also, object types hide implementation details, so that you can change the details without affecting client programs.
Object types allow for realistic data modeling. Complex real-world entities and relationships map directly into object types. Moreover, object types map directly into classes defined in object-oriented languages such as Java and C++. Now your programs can better reflect the world they are trying to simulate.
More detail u can get in Oracle docs. I have just taken out few theoretical parts to explain basic oops concept in Oracle..