Histograms are extremely helpful in displaying data. Not only can they present data but they can be used to check exposure on the LCD screen of your DSLR. Sometimes the exposure can be inaccurate depending on the brightness of the screen and the light hitting it. The only way you will truly know if your image is correctly exposed is by reading the histogram.
Steve Perry examines more carefully what histograms are and how you can use them to your benefit. In the beginning of his video he explains how to set your camera up to display the histogram and later goes on to explain how to read it. He also highlights the importance of the histogram and how it can ultimately ensure that you are not losing detail in your image.