The little screen on the back of the digital camera is the LCD, or Liquid Crystal Display. Most LCDs are between 1.8 and 3.0” diagonally using modern TFT technology. They can act as a large screen viewfinder, but are also used to review images or adjust camera settings. Since many digicams use a menu system to choose between different options or functions, the abundance of switches on the camera can be significantly reduced.
To make sure the LCD screen can be used in bright outdoor conditions, the better ones are coated with an anti-reflective layer or have a reflective sheet behind them.
Many users choose to frame the scene by using the LCD because they are much more accurate than conventional viewfinders. They don't suffer from parallax error and show almost 100% of the actual recorded image. Another advantage is that some can be angled up or down for taking pictures at awkward angles. They allow you to get close to the ground or you can keep the camera high above you to look over people's heads in a crowd, while still being able to compose the image by looking at the LCD screen. It should be noted that if you need to use the LCD a lot, or if your camera lacks an optical viewfinder, a spare battery would be advised.