From The Verge, a new-ish tech site, a mega-guide on everything you need to know about buying a camera. It starts at the beginning with the basics of photography, goes over ISO, aperture, shutter speed, megapixels, white balance, and the major types of camera.
If you’re new to digital photography, the three things you should acquaint yourself with first are the ISO, aperture, and shutter speed. The three work in concert, and if you can manipulate and control them all, you’ll take fabulous photos without even touching the rest of your camera. Together, they’re known as the Exposure Triangle, because they control how much light you’re exposing the camera to (aperture), how sensitive the camera is to that light (ISO), and how long your exposure lasts (shutter speed).