Smalltalk is an interesting language in many ways. Classes in Smalltalk do not have a direct textual representation, but are instead viewed using a tool called the browser. The browser allows the programmer to select a category of classes, a specific class, or a specific method within a class. The information selected is then displayed in the bottom panel.
More information on Smalltalk can be found in the textbook. However, many features differ from one platform to another, and so it may be necessary to consult a reference manual for your particular system.