Sounds complex and is if I were to try to give you a technical explanation…but this will be the simple explanation.
The fancy camera makes an image based on how much light it gathers, for how long it gathers that light and based on how sensitive the film or sensor is to that light (That is called ISO).
So…most cameras have a setting on the little top dial that says T or S…for Time or Speed. Same thing. You can tell your camera to let light into the camera for as long as you want…from just 1/8000th of a second (if perhaps you are shooting in absolute bright sunlight) all the way down to hours of exposure using the B for Bulb setting on the camera which allows you to keep the lens and camera gathering light until you manually stop it from gathering light (for perhaps an ultra long exposure of the deep sky to gather enough light to reveal something like the rings of Saturn). If you shoot anything slower than 1/80th of a second, you must use a tripod or you will get a shaky image. Many people will tell you that you can shoot at 1/60th of second hand held, but 1/80th is safer. In fact, CJ, Linda and I use tripods for the majority of our shots no matter the speed…steadier platform for shooting and more comfortable for the photographer.
If you want to get a stop action shot of a flying bird…you need to be shooting at 1/1000th of a second or faster…which means you probably need a lot of sunlight. If you are shooting any kind of action…like sports action or a moving car or running animal…, try for 1/1000th or faster.
A landscape or portrait during daytime…1/500th might be a good setting, but you can go all the way down to 1/80th of a second without a tripod.
A sunset or sunrise photo of water moving…to capture enough light for the sky and foreground and to make the water look like it has some movement…about one third of a second with your camera on a tripod.
The Milky Way at night…ten to 30 seconds on a tripod. Anything more than 30 seconds and the stars will start to have trails and not be pin points. Shoot for ten minutes in the that B or Bulb setting and you will start to have some interesting looking star trails.
So…the first lesson of controlling something is to control it with speed or time. Set your ISO at 100 or no higher than 400. Turn the little dial on the top of your camera to T or S and then follow those basic guidelines above to get your shot. You will have controlled the speed of the shot and the ISO the camera will use…and the camera will choose the right aperture or opening of the lens to make all that work. That is taking control…and almost as good as shooting in M or Manual…but we will get to that eventually. Aloha.