The best thing you could do is take a local photography class and learn to use Manual Mode because then when the camera is set to AV (Aperture Priority) or TV (Shutter Priority). you will know the results. Aperture is your lens opening.

For every shutter speed there is a correct aperture and vice versa. There is also what is called the Sunny 16 Rule which is the starting place on a sunny day. If you set you camera at f16 and your shutter speed at 100 with the sun facing the subject this would be the camera setting.

If things/people are moving you want a faster shutter speed so your aperture would need to be open more. All to let in the right amount of light for the exposure.

Think of it like a recipe. You start out with half a cup of liquid and half a cup of flour. Some recipes need more liquid and some need more flour.

A good book for beginning photographers is called the Kiss book of photography.