The Word photography comes from a greek word of Phos( which means light), and graphe (which means drawing) therefore the definition of photography is "drawing or Painting with light"
The most basic technical aspect in photography is the exposure where this determine how the camera sensor takes up information of light that bounce off an objects creating images containing color, tone, lines, etc
You will need to learn the connection between 3 fundamental component of exposure in rder tounderstand the basic theory of taking photographs. Those are ISO, Shutter Speed, Apperture. Those relationship can be defined by exposure Triangle. but first lets understand each of those component as an individual.
ISO.
In the old days when camera still use a negative film, ISO is the sensitivity of the film towards the lights that cames forom the lenses. the higher the sensitivity of the film, the more noise you will get in the image, Hence the image is not sharp.
In the digital world, your camera are able to have an ISO range 100-3200, being ISO 100 is the sharpest in terms of image quality and 3200 has the worst image quality. But noise is not necesserily wrong. In the old days the quality of the film is not as good as it is now ( before digital) so if you want your photo to have an old or antique feeling, you might want to shoot using high iso.
Apperture
An apperture is the diameter of the lens opening where it is being controled by 2 shutter curtain in the modern DSLR camera. The lager the diameter of the aperture, the more light reaches the sensor. Apperture is expresed as F stop in the photography terms. it can have range of F1.2 ( the widest aperture ) to F33 ( the smallest aperture).
In term of image result, aperture determine the depth of field in the image. That is the distance of the the object in focus. The higher the F value , the longer the depth of field, the smaller the F value the shorter the depth of field.
Camera aperture F2.8 Camera aperture F 13
Shutter speed
Shutter speed determine How fast is the camera exposure to the light. the brighter the object, the faster the shutter speed of a camera to get a good exposure.
Camera speed 1/160 Camera speed 1/2500
To see animation of modern camera shutter follow this link
HMPix photography