Is exposure correct for this luminance histogram? What does this say about the dynamic range of the scene?
That is what's known as a histogram. The exact meaning requires more context. It could either represent the light intensity from left to right across the image or, based on what the plot looks like, it more likely indicates the amount of the image that falls in any particular luminance (brightness).
Assuming it is the later, which it appears to be, then the dynamic range of the image is pretty limited as the majority of the image is not making use of the brighter or darker portions of the color space (the total amount of colors that could be produced).