Frame vs View
The image below shows the difference between a Frame and View windows when using a MFC Frame/View architecture.
On the MFC Frame/View architecture, each document can be linked with one or more View. The View is nothing more that a representation of the document.
You can have the same document presented in several different formats by using one View for each format presentation.
A View will always be inside a Frame and a Frame can have more the one View.