TechRadar: The A to Z of Photography: Viewfinders
Many cameras have viewfinders, even though they have a screen on the back for viewing and composing pictures. In fact viewfinders are considered a must-have amongst enthusiasts and professionals, partly because they’re much easier to use in bright light where regular screens can be hard to see, and partly because for many people it’s more natural to put the camera to your eye than it is to hold it at arm’s length.