One came with the camera, the other came with the accessory pack. The higher density cards are currently in short supply. I do not suggest using the LCD display for this purpose under battery power. Do not use older 650 mAH low-capacity niCd rechargeables. Do not use non-rechargeable alkalines unless you are willing to pay through the nose or unless you are really frugal with your LCD display use and use the AC adapter whenever possible.
All digital cameras eat batteries for lunch.
When comparing a digital camera against a standard 35mm SLR, my professional-photographer uncle says that 35mm film holds between 60 and 80 MBytes worth of data. Consumer level digital cameras thus have a long way to go. They are great as long as you don't enlarge the image. If you intend to make larger prints, stick with 35mm film for now. This is a camera company, not a printer or CCD video egg company making cameras.