The heading should really say Frame or Picture or Out, because what follows applies to all of them. I will use "picture" with a small p throughout this page.
There are three basic views: Full, Normal and Magnified. You can cycle through these views by pressing the Right Mouse Button. Sometimes you will only be able to make two of them appear. This occurs when the magnified view would require shrinking to fit it on the screen, a contradiction.
Full View can be reached from any other by pressing A. Now the whole picture will be shown, shrunk if necessary so there is no need for scroll bars. If you drag a rectangular box around an area, that area will be surrounded by a dotted line and will become the Active Rectangle. Pressing A repeatedly selects the full picture, the original sized picture when loaded, a suggested clean rectangle (that is, without messy edges), and the last Active Rectangle as defined above. For information on what you can do with these Rectangles see Rectangles. It is these areas that are used by the commands that save Rectangles on the File menu. In this view there is a narrow selection margin all round.
Normal View does not shrink or stretch the picture; every pixel on the screen represents one pixel in the picture. You can always reach this view by pressing the Right Mouse Button enough times. If the whole picture will not fit in the window, scroll bars will appear. To make inspecting the whole of a picture easier, Home will take the view to the upper left corner and End to the lower right corner. Page Up moves the view one page up and Page down moves in the opposite direction. Control+Page Up moves the view to the left and Control+Page Down to the right. If you press the Left Mouse button and drag out a rectangle, that will become the Active Rectangle and the view will immediately switch to Magnified View where you can edit at the pixel level. When in Magnified view pressing the Right Mouse Button once will bring you back to this view.
Magnified View can always be reached by pressing the Right Mouse Button enough times, provided the Active Rectangle is small enough. There must be at least a one to one correspondence between pixels in the picture and those on the screen. You may get a distorted view of the picture because pixels are stretched independently horizontally and vertically, e.g. a pixel in the picture may be represented by a 2x1 rectangle on the screen. This is to make the pixels easier to see and hit when editing them. You can also reach this view by drawing a rectangle in Normal View as explained above. As well as allowing you to examine parts of the picture at a large scale, this view allows you to edit individual Pixels.