A histogram is a graph of the exposure of each image and can help you determine if images are over or underexposed. The ‘true black’ is illustrated at the far left of the graph and ‘true white’ is found on the far right. A well-exposed image will generally show points close to both ends. Each histogram graph tells a story about the exposure of the image and can guide you in making adjustments so that images are properly exposed.
For winter shooting, a histogram can be very useful in showing if bright white snow is spiking your exposure and causing your image to appear ‘blown out’ or overexposed. If this happens while you’re shooting, you can trick your camera by adjusting your +/- compensation button to adjust for this situation. And, if you’re shooting in RAW format, you’ll have the ability to adjust your highlights and mid-tones in post-processing if necessary. That said, it’s a lot easier to get the shot the way you want it the first time as opposed to having to make corrections at a later time.