Optical Zoom: This number tells you how much larger the camera can make its subject appear simply through a slide of the lens. In other words, a camera with 3X Optical Zoom can make a subject appear 3 times larger in the frame. Optical zoom is generally preferred to digital zoom, since it can magnify an image without losing picture quality.
Memory Type: Although some cameras do have some memory built in, most users benefit from using higher capacity flash memory cards to store more pictures and/or longer videos. Generally speaking, Digital SLRs and the more advanced standard cameras use CompactFlash and Microdrive cards, while the rest use either a form of Memory Stick (Sony), xD-Picture Card (Olympus & Fuji), or Secure Digital Card (most other brands). Many cameras using xD cards also use SmartMedia, as many SD compatible cameras can also use MultiMedia Cards (MMC).
LCD Screen Size: Digital Cameras generally have a miniature LCD monitor on the back to preview pictures that have been taken. LCD Screen Size is the length of that monitor measured diagonally.
Weight: Weight of the digital camera including memory card (if applicable) and batteries. SLR camera weights are body only.
