Scary thoughts when starting out - it took me a while to understand how everything is connected but when you will understand this, you will be wondering why the hell it looked so complicated. Luckily, I did not have to see a guru on a remote and hidden mountain to understand this - Internet is FILLED with resources (most of them free) explaining how stuff works, if you scroll until the end, there is a neat video for you. The photography community is quite strong on youtube and I strongly suggest subscribing to some of the people out there.
In short :
Shutter : Controls Ambient Exposure (available light) - or How long does light comes in
Aperture : Controls Flash Exposure and depth of field ("created"/flash light and out of focus image)
Iso : Light Sensitivity (Higher is usually worse)
Problems that all those 3 might give you (well some of the problems I ran into) with examples;
Shutter : Blurry image
In this case, shutter was not fast enough for the amount of ambient light (dark wedding room) so you cannot only see blurs.
Aperture : Overly dark or overly bright image
|Aperture (3.5) was way too high for the flash so once again, you cannot see anything.|
ISO : When too high, grains appear in dark places (cell phones are fantastic at this)
|See the mutty/grainy blacks in the photo? That is what we are trying to avoid.|
All of the 3 items mentioned before are in relation and will help you understand how your camera's manual setting work. The all work in a triangle. Lower your aperture and you will need to increase your ISO. Increase your shutter and you will need to decrease your aperture to compensate.
The video below is what unlocked in my little brain how my camera really functioned. Take out your photo note pad and start learning...now!