Photokeeper has four basic views: Page View, Photo View, Slideshow View, and Zoomed Thumbnail View. You can flip between these views by clicking on their corresponding buttons on the main toolbar.

Clicking on these buttons will display the corresponding view in the main window pane (the largest area of the window).

There are also two other special view-related buttons. Fullscreen enters fullscreen mode, which you can leave by pressing Esc or F11. Fullscreen Slideshow does the exact same thing as if the Slideshow and Fullscreen buttons were pressed separately.