Everything piled up against the right edge means highlights blown out, lost detail.

Clouds become white blobs.

Bad histogram, everything piled up against the left edge.

Right.

Bad histogram.

Everything piled up against the left edge.

Three photos, normal, slightly darker, slightly brighter.

Look at them afterwards.

Which looks most like what your eyes saw?

The answer is often surprising.

Histograms without the scary bits.

Photographers obsess over histograms.

Here's all you need to know initially.

A histogram is simply, open quote, a graph showing how bright the image is.

Close quote, left side, dark.