CLASS : A class defines object properties including a valid range of values, and a default value. A class also describes object behavior. A class is a logical entity. A Class Diagram will show what the Objects in your system consist of (members) and what they are capable of doing (methods) mostly static.
OBJECT : An object is a member or an "instance" of a class. An object has a state in which all of its properties have values that you either explicitly define or that are defined by default settings. An object is a physical entity. An Object Model Diagram shows the interaction between objects at some point, during run time.
Example : Bicycle is a class then MountainBicycle , SportsBicycle , TouringBicycle , etc can be considered as objects of the class.