The Histogram in Lightroom classic

What Does It Tell Us

A Histogram is a graph of different tones in your image and gives us information about the exposure range of our image from blacks to whites and everything inbetween. It allows you to adjust the blacks, shadows, exposure, highlights and whites of your image. It is found in the upper right hand corner of the screen

Clipping

In photography and video, clipping refers to certain areas that fall outside the minimum and maximum intensity that can be captured. In other words, there isn't any information in that part of the image. Lightroom represents these areas with blue for black clipping and red for white clipping. The two triangles on the top corners of the histogram show these areas when selected.