All photo cameras from the simplest to the highest of high tech share some basic features.
Lens. The lens is made up of layers of glass which are each shaped to focus incoming light onto a surface used to expose the image.
Light sensitive medium. In digital photo cameras this is a sensor – which comes in a variety of types but all basically change light into an electrical signal. In film cameras, the exposure takes place on, you guessed it, film.
A variably sized hole call the aperture. Located in the lens, the aperture control is a series of blades which changes the amount of light passing through lens. The aperture’s basic unit of measurement for how much light is getting through is the “ƒ Stop.” A whole Stop change in aperture lets in either half as much light or twice as much light. On your lens (or in the view finder, or maybe on an LCD menu on your camera) you typically see numbers like ƒ1.8, ƒ2.8, ƒ4, ƒ5.6, ƒ8, ƒ11, ƒ16, and ƒ22. These are whole Stops which, as previously explained, lets in twice as much or half as much light compared to the Stop beside it.
A shutter which limits how much time light is allowed to enter your light-tight box. The measurement for the shutter is the “shutter speed,” also known as Stops, which is measured in fractions of a second like 1/30th, 1/60th, 1/125th, 1/250th, 1/500th and so on. You can see a little easier how each might vary the exposure by either half as much light, or twice as much. Exposure times can also vary from 1/8000th of a second to several seconds. Some systems can use up to hours of exposure