On a regular camera, you look through an optical viewfinder to frame your shot. This is the same technology found in flat panel displays or digital watches. On a digital camera, an integrated LCD screen can range in size from 1.8-3.0 inches measured across the diagonal.
Many cameras rely on the screen as the sole viewfinder.
There are a few drawbacks to cameras that only have LCDs. With a LCD, you can frame shots more accurately, but you need to hold the camera at arm's length from your body. If you're shooting a lot your arms can tire, making your grip shaky. LCDs work well with static shots, but some LCDs can't update quickly enough to capture fast in-motion objects. Shooting outdoors can also pose a problem because the screen will wash-out in direct sunlight.