Moving your viewpoint in to get a closer view of your drawing data is called zooming in; moving your viewpoint back to get a more expansive view is called zooming out. Moving your viewpoint to another part of your drawing without zooming in or out is called panning.
Changing your viewing position lets you do detailed work on tiny objects and then zoom out and move around rooms, houses, or neighborhoods from an Olympian perspective. Early versions of AutoCAD included a sample drawing of our solar system, drawn to scale with kilometers as units, which proved this. If you zoomed all the way out, you could see Pluto's orbit (yes, kids, Pluto was a planet back then), and you could zoom in close enough to Earth's moon to read the inscription on the plaque left by the Apollo 11 astronauts!
Panning means changing your viewing position without changing the magnification of the view. If you zoom in enough that some of your drawing no longer shows up on-screen, you're going to want to pan around — move left, right, up, and down in your drawing — without zooming in and out. AutoCAD makes panning easy with scroll bars and realtime panning. And in case you're wondering what realtime panning might be (as opposed to pretendtime panning, maybe?), it simply means you can see the objects moving around the screen as you drag the mouse up and down or back and forth. (Of course, it's your viewpoint that's moving, not the objects!)
Both panning and zooming change the ...