This is the duration that the shutter stays open to let light shine onto the sensor. The higher the speed, the shorter the duration. In bright environments, a faster shutter speed is used because too much light would be captured if the shutter remained open for too long. In darker environments, a slower shutter speed is used to allow the sensor to be exposed.
It is similar to drawing a line using a pencil whereby a dark lead (more visible) needs just one pass whereas a light lead (less visible) needs multiple passes. An ocular parallel can be seen in the way we need to move slowly in the dark because our eyes need more time to register our surroundings than they do in the light.
Sample image is a crop of a snow plow displayed on the screen of a BlackBerry Z30.
This tells the sensor how much to amplify the light it receives. Bright environments need less amplification so low ISO sensitivity is used whereas higher ISO is used in dark environments to amplify the available light. Most cameras use ISO 100 or 200 for daylight and ISO 800 or 1600 for night scenes.
While most resources mention ISO when describing high-end cameras' ability to capture better images in the dark, I have found that it can be useful in bright scenes as well. Setting a low ISO and descreasing the shutter speed can give some images more balanced lighting and sharper lines. Being able to set a lower ISO in a night shot compared to what the auto setting would use can also reduce noise.
Following is what allowed me to gain some insight into these features
I hope these tips help get you started on your Priv-powered, professional photography projects.
Below is a crop of the "real" original image (not displayed on a Z30 like in the samples above). This was taken using a Z30 which used auto settings (Shutter 1/10 and ISO 750).