What is the differences of a Nintendo DS Lite and a regular Nintendo DS

the ds lite is smaller and the stylus (pen) is a little better. the screen sizes are the same on both. the normal ds isn't sold any more so youll have to buy it used
The DS Lite is lighter, smaller, and has an extended battery life. The DS Lite no longer has backlight control through the main menu; instead, the DS Lite has 4 levels of brightness. The Power Button is now a slider; the stylus slides into the sides rather than the top. The start and select buttons have been moved to the bottom part of the console. GBA games extend past the Lite's bottom edge due to their size.

http://en.wikipedia.org/wiki/Nintendo_ds_lite#Differences_between_the_DS_Lite_and_the_original_DS