Let’s preface this with the fact that the most important part of your camera is the 8 inches behind it.
There, that is done.
On your camera though, I might argue that Exposure Compensation is a button that everyone should know where it is and how to use it. Your camera will decide for itself how bright or dark a scene should be, most of the time it is right…but sometimes it is wrong. Especially in high contrast scenes or where there is a lot of black or white in the scene (like snow!!!) Exposure Compensation allows you to influence the cameras decision. We can make the image brighter by letting more light into the camera or darker by letting less. The (+) side of this graph/meter/diagram/thing will let more light in (plus is more, right) and the (-) side will let less light in (negative is less, this is easy.) Look it up in your manual (yes your manual, it is that book that came with your camera) and/or look for this icon on your camera.
Below is the same scene with different exposure compensation amounts; the top image is with no Exposure Compensation (a zeroed meter) the next with +1 and the bottom with -1. Which is better?
Which is better? That is personal preference, this is an art remember.
In the beginning it takes experimentation, not knowing if you need more light or less. Soon you will know if you just need one over the other. Digital makes it easy.
Below are a couple images where I had to let in more light to allow my subject to be "exposed correctly." (Key point: pay attention. I said subject. Subject is the thing that matters.) This is because there is something bright in the scene that my camera thinks is important so it dims down the exposure...but I don't want it too.
1) Your LCD on the back of your camera can look brighter than it actually in is low light, and it will look darker outside. Maybe we will talk about the histogram sometime.
2) Oh, and don’t forget to reset your meter! Otherwise if you set it to +1 and forget, later your images might be too bright when you don’t want it to be.