Objects

Much of the power and flexibility of modern software analysis and design derives from its use of objects.

Classes

Classes create an abstract representation of the world, letting you discard unnecessary details.

The 3 properties

Class

1. properties

2. behavior

3. relationships to other objects

Object

1. state

2. behavior

3. identity

Ref: http://javadevwannabe.blogspot.sg/2012/02/state-behavior-and-identity.html?m=1