To help to understand the difference, Erik Reinhard - on of the pioneers of HDR imaging - wrote an article about "Flickr HDR" which is worth reading.
If you want to be able to master the various problems and pitfalls of HDR, you have to be able to understand exactly, what type of image you're actually working on. I personally prefer to distinguish between 3 types of images - each one with important differences in workflow (e.g. tonemapping):
- LDR: That's what you will certainly use most of your times. It is the range, your camera can capture with one shot (no matter if you use JPEG or RAW).
- MDR: Images with extended range, typically a bracketed image. Still, this image will not contain the full dynamic range of the scene you capture.
- HDR: This is "The real thing". Everything (all brightness and color), including the light source itself is included in the image. Thus, such images can even be "reversed" by using them as a light source, e.g. for computer generated scenes - called image based lighting (IBL).
- Flickr HDR: http://www.flickr.com/search/?q=hdr
- Real HDR: http://hdview.at/hdr/index.html, using