Object reference

• An Object is an instance of a Class, it is stored somewhere in memory
• A reference is what is used to describe the pointer to the memory location where the Object resides.
• A variable is a means by which you can access that memory location within your application (its value is "variable"). While a variable can only point to a single memory address (if its not null), it may change and point to different locations through out the life cycle of the application

I wanna know some definition about it

Hey Sina, so an object reference gives us a way to access properties and methods associated with a specific object. Often, it will be stated as just passing an object. It means the same thing, it's just that technically speaking we don't work with objects, but instead we work with a reference to the object, which is to say an object reference. If you understand what it means to pass an object, then you understand what it means to pass a reference to object; at least for the sake of understanding what's going on.

Note however, understanding a reference is fundamental to object oriented programming.

Hope that helps. Best ~