Digital cameras store their captured images in internal memory or on some type of removable media. If the camera stores it's images internally and the memory becomes full you must either delete some of the images to make room, or connect the camera to a computer and transfer the files. This can be very inconvenient. This is very convenient. There are several types of removable media in use today.
Most digital cameras have an optical view finder.
The LCD lets you see how your image if framed before you take the picture. It also allows you to review and manage images stored on the camera. LCDs are often more accurate for framing shots than the optical view finder found on the camera. The main drawback is the power it consumes. You wouldn't want a digital camera without a LCD, but the optical viewfinder can be nearly as important.