Views organize information in various convenient ways. For example, the Outline view shows you a list of all the function names when you're editing a C file in the C/C++ editor. The Outline view is dynamic; if you declare a function called mynewfunc(), the Outline view immediately lists the function.
Views give you different presentations of your resources. For example, the Project Explorer view shows the resources (projects, folders, files) you're working on. Like individual panes in a large window, views let you see different aspects of your entire set of resources.