@Patience55: I’ve found once you’ve rendered something you can switch between the wireframe and the rendered image by pressing the Esc key.
The thumbnail sketch is the Nano Preview Pane, which shows a smaller version of what you’re doing in the main window. It’s good to use in helping place items in the scene or to get a iffy idea how the scene looks. The arrow on the bottom right of the Nano pane lets you choose how you want things displayed in that window.
I think the ‘+’ and ‘-’ you’re talking about, those two items on the bottom right of the screen? They are for zooming in and out to whatever parts in the scene. Zooming is good if you’re trying to get something small placed correctly or make sure something lines up correctly, or for whatever reason you may choose. Zooming out gives you a better overall view of you scene, and again, for whatever else reasons you choose.
By the way, that second image looks interesting.