You can use a class module to create a definition for a new custom object. When you create a new instance of a class, you create a new object and return a reference to it.
Any public procedures defined within the class module become methods of the new object. The Sub statement defines a method that doesn't return a value; the Function statement defines a method that may return a value of a specified type.
Any Property Let, Property Get or Property Set procedures you define become properties of the new object. Property Get procedures retrieve the value of a property. Property Let procedures set the value of a nonobject property. Property Set procedures set the value of an object property.
For example, you can use a class module to create an interface layer between your application and a set of Windows application programming interface (API) functions that it calls. To do this, you create a set of simple procedures that call more complicated procedures in a DLL. When you create an instance of this class, the procedures you've created become methods of the new object. You can apply these methods as you would the methods of any object, and in doing so you also call the API functions.