In Ruby, everything is an object. All objects have a unique identification; they can also maintain a state and exhibit behavior in response to messages. Normally, these messages are sent out via method calls. A Ruby object is a string, for example.
An object is a member (or instance) of a class, and objects have the class's behaviors. The object is the program's actual component, whereas the class describes how instances are formed and behave. A method is a type of operation that an object can execute.