Don't get too intimidated with the buttons since you don't have to use all of them, just remember some of the basics. I got a Rebel T2i so I think I can help you but I'm definitely no expert. See the dial? I just keep it to M (for Manual) since I don't really see the need for others. The last one is video. If you're shooting video, the start/stop button is the little button next to the viewfinder with the red dot next to it.
F-stop: This is how open the lens aperture is. A lower F-stop allows more light while a higher one does the opposite. High F-stops are recommended for bright sunny days and affects "depth of field", how clear the focus is.
Shutter speed: Also known as exposure time. It's how long the lens stay open as it takes the picture. Example: 1/125 shutter speed means that the lens is open for 1/125 of a second; in other words it's how long the "film" is being exposed to light. Anything slower than 1/60 (for example, 1 second) is best recommended to use with tripods and hopefully a still subject. Faster speeds can eliminate motion blur. Imagine people running. At low speeds, the legs will appear blurry while at high speeds, legs will be more clear as if they're in a "freeze frame".
How your pictures look depend on the combination of F-stop and shutter speed. It's a bit tl;dr so I recommend reading this:
http://warhorsefilmmaker.tumblr.com/post/2905210557/quinns-guide-to-iso-f-stop-and-shutter-speed-for
ISO: A low ISO means you need a lot of light. Higher lets you take pictures in dark areas but at the cost of "noise" or film grain. Having film grain isn't the end of the world but I prefer to keep it as low as possible like around 400.
If you see a gauge that says -2, -1 ,0 ,1 ,2; that's an indicator that tells you if the shot might be too bright or too dark. 0 is ideal.
If you use a viewfinder, the beeping and lights flashing tells you the subject is in focus. IMO, I find it more accurate than using the screen but that's just me.
As for the flash, it's very bright so keep that in mind as it can ruin pictures. A diffuser can make it less harsh.
Most importantly, just practice. Combine different F-stops and shutter speeds and compare the results. Hope this helps.
