As a web developer, you are familiar with the concept of a page which originates from the early days, when such pages where static resources that had links to other pages. The concept of a page is excellent when you are implementing a web site, but creates lots of work when creating applications. Take for example a dialog scenario which is implemented over web using two disconnected pages bound together through a client side script.
Imagine that creating a dialog was as simple as creating an object, calling its methods, and setting its properties. This is exactly how desktop developers see dialogs. This concept is called forms. A form represents a window which can have child forms, which are windows as well. It sounds outrageous; that when you create a page it needs to have a script, which in turn opens a new browser window with a second page, which receives arguments and displays user interface, which then, uses a script that is used to callback the parent page… all that, while a desktop developer simply creates an object.
When you are working in a single object oriented layer, you are also able to implement many useful design patterns, such as the observer design pattern. This means that when objects need to interact with each other they only need to post an event to the form and other objects will subscribe to that event saving you the hassle to explicitly bind events between controls. Just to underline the difference, the same task in the web scenario would require multiple cross referencing scripts.
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