On your digital slr camera you have certain settings you can take different types photographs with, the main settings you will use are 'auto', 'manual', 'aperture', 'shutter speed' and 'programme', the setting 'auto' will automatically adjust everything needed to your surroundings e.g focus.
Manuel (M)- this setting is a DIY setting, you have to adjust your shutter speed and aperture yourself, this allows you to have an image you want and not the camera.
Aperture (A) - this setting allows you to set the aperture to whatever you want and have control but the shutter speed is set to automatic, the aperture determines the depth of field, the higher the 'F' number the more narrow aperture but the greater the depth of field, the lower the 'F' number the wider the aperture the more narrow the depth of field.
Shutter Speed (S) - this setting decides the shutter speed and the aperture is set automatically, the shutter speed determines how much light is let in before the picture is taken, the quicker the shutter speed the less light let in and the longer the shutter speed the more light will be let in.
Programme (P) - this setting will decide your shutter speed and aperture based on your surroundings.