If you have a local library go and borrow a few books on photography. Or join a good photography forum that caters for beginners.
If you are shooting into a bright light source such as the setting sun over the ocean, your camera will shift exposure to try and turn that bright part of the scene into an 18% grey area. This invariably causes the rest of the scene to be under-exposed, which may not be what you are trying to accomplish, so you can compensate for this by using the + compensation, which over-rides the camera meter by however many stops you need it to.
Then again if you don't want to blow out the highlights you don't want to compensate too much, so a trick is to "bracket" about 7 different stops of exposure and then blend them in an editing program to retain both highlights and shadows.
High contrast scenes will always fool even the most advanced cameras. It's the photographer who needs to do the thinking in those situations. Of course it helps to have a DSLR with a high dynamic range like the Nikon D3/700.