SLR - This is the single lens reflex, this means when your viewing and object through a manual camera the light from the source hits the object your taking a picture of, and then hits the mirror inside the camera which rotates the image for your eye to then see.
Aperture - The aperture is the opening which is on the camera, the lower the f stops the larger the aperture goes, and the same if the f stops are larger the smaller the aperture then goes like a human eye.
Shutter Speed - the shutter speed controls the time to which the photo is exposed to light such as the slower the shutter speed the more light gets into the picture. If the the speed is set to fast then there will be less light.
Depth Of Field - This is how much sharpness there is between the background and foreground such as the lower the f number and the larger the aperture the smaller the depth of field