iPod has backlighting, so you can see the display in low light.
You can configure iPod so the backlight turns on for a set amount of time when you press a button or move the scroll wheel.
To access the backlight settings:
A backlight on/off switch can be added to the Main menu by selecting:
Settings > Main Menu > Backlight
With iPod models prior to Fifth Generation iPod and iPod nano, you can also press and hold the Menu button down to toggle the backlight on or off. Find out which iPod model you have.