The histogram is a bar graph that shows the range of brightness that make up an image. The histogram tool is a very useful tool in Photoshop because it make editing images much easier by allowing it to become harder to allow other adjustments to get out of control and harming your the image your working on instead helping it.

The hue/saturation tool can be very helpful when editing images because this tool allows you to be able determine how vibrate the colors appear in your image that you are working on.