It's just DVD with slightly improved picture.
No matter how many times people say this it simply isn't true and the numbers back it up.
* A widescreen DVD puts 345,600 (720 x 480) pixels on the screen, while a widescreen Blu-ray puts 2,073,600 (1920 x 1080) pixels on the screen. With a proper source, the amount of detail in a Blu-ray picture is astounding when compared to DVD.
Then add to the fact that Blu-ray has deeper colors, better audio and interactive features, I'd say the jump from DVD to Blu-ray is far greater than the jump from VHS to DVD. It's non-sense that people try to equate DVD and Blu-ray simply because they're both disc based formats.