Hiding the complexity of a application from the end user is Abstraction. Assembly language is abstarion of machine and language like Basic,fortran,c are the abstraction of assembly language.
The programmer represents elements (elements of application or problem) in problem space. Elements in the problem space and their representations in solution space as object. Object is a instance of class.
OOPS allow us to describe the problem in term of problem rather then in term of computer wh
ere the solution will run.
In case of “Bank teller problem”
The member of each class share some commonality every account has a balance, every teller can accept a deposit etc. at the same time each member has its own state each account has a different balance, each teller has a name, thus the teller ,customer, transaction can be represented with a unique entity in the computer program. This entity is the object belongs to a class that defines its characteristics and behaviors.