HDR = High Dynamic Range. This technique has to do with stacking multiple images of different exposures on top of each other, followed by Tone Mapping. There is a lot of confusion between the two.

Take a look at these 3 images, especially the cargo hatch of this helicopter.

This first would be a normal exposure. Do you see how the detail of the cargo bay is lost?So you take a second exposure to get the details of everything in the shade.And a third to capture details in lost highlights.Stack them together in PS and then Tone Map. Its a lot of fun. There are a lot of tricks to doing this and making it work right. Itll be on the DVD,