TIP #3: When setting up your manual camera settings, set your shutter speed third.
The shutter speed is how fast or slow the shutter on your camera opens. The shutter is in your camera body, not your lens. It opens and closes when you press down the button/shutter and allows light to come into your camera. The shutter is what makes the clicking sound when you take a picture. That sound is the shutter opening and closing.
Shutter speed is shown in fraction form. The fraction is referring to the 1/15 of a second (slow) that it takes the shutter to open and close. Or the 1/6000 of a second (fast) it takes to open and close.
A slow shutter speed allows more light to come in because the shutter is open longer. But since the shutter is opened longer it also allows for some movement in your picture (motion blur) if it’s open longer than 1/80 of a second and there is a moving object/child in front of the camera. Continue to learn more about shutter speed here.
I would recommend setting your ISO on your camera first (based on the lighting), then your aperture second (based on the creative look you desire), then your shutter speed third (to get correct exposure).
This image below was shot with a shutter speed of 1/1600 second. That is a relatively fast shutter speed. I chose a fast shutter speed because it was a very bright day and I wanted to get correct exposure on my image (not have it be too bright) and also because I wanted to capture him mid-kick.