The View menu enables you to look at your document in different ways. You can see how your image will appear on a different monitor or a simulated press. You can view the colors that are out of range of your color space. You can zoom in and out or view the printed size onscreen.
Proof Setup: Preview your image in different modes. Setup simulates a Mac or Windows monitor display or a printing press's color space.
Proof Colors: Simulate your document colors in the window depending on the options.
Actual Pixels: Zoom your image to 100% to see the actual pixel image.
Print Size: Zoom your image to the size onscreen at which it prints, using the resolution settings for the image.
Show, Layer Edges, Grid, and Guides: Layer edges, the document grid, and guides all help with visual alignment. Show or hide these nonprinting elements to help you get precise positioning. The grid looks like graphing paper lines overlaid on the image. Guides are the custom vertical and horizontal lines you created by dragging from the rulers into the image. If guides are hidden, you see the guide as it's positioned, but it becomes invisible when you let go of the mouse button.
Rulers: When you show rulers they appear at the left and top of your document. Click, hold, and drag from the rulers into the document to create a guide. If you want to remove a guide, make sure it is unlocked and drag it back into the ruler area. Set the ruler measurements to inches, points, picas, and so forth in Photoshop's preferences.
Snap and Snap To: When Snap is selected, the elements you move across the canvas have a magnetic snapping effect when brought into the same zone as the objects in which snap is activated. Under Snap To, you can give the grid, guides, layers, slices, and document bounds. Snap to Layers causes objects on separate layers to have a magnetic property to them, which is helpful for alignment purposes.
Lock Guides and Clear Guides: When guides are locked, you are not allowed to move them after they have been initially dragged onto the screen. To move the guides again, select this option again. Clear Guides take out any guides you created. After guides are cleared they are deleted completely and have to be re-created if desired.
Lock Slices and Clear Slices: Slices that you draw in Photoshop can be locked. This prevents accidental movement or sizing. If you have this option checked in the beginning, you are unable to create any new slices.