Here’s a basic introduction to digital photography. it’s nicely illustrated, if a little short.
If you’re buying a digital camera, do consider the cost of buying the necessary accessories as well:
Sufficient Storage Media
These come in various formats, eg. Compact Flash (CF), Secure Digital (SD), Memory Stick and many others. Usually the one that comes bundled with the camera is insufficient. I suggest a minimum of 2GB for a 6 megapixel camera, or 4GB for 10 megapixels. The more megapixels, the faster your storage media will fill up.
Not absolutely necessary but handy since digicam batteries drain notoriously fast. If your camera uses a proprietary lithium battery, you need to get at least an extra one. If it uses AA batteries, get rechargeable spares which are cheap compared to lithium. AA batteries are also easily available even in remote areas, though you’d probably only find non-rechargeable types when on an island vacation.
CD or DVD writer
This is because digital cameras don’t produce negatives like film cameras do. So you’ll need a way to backup your precious photos, in case your hard drive crashes.