Exposure Compensation is a tool that is available on almost any camera, from camera enabled phones, to high end DSLRs.  The use is pretty simple in most cases, and on most cameras.

If you have ever had a situation where the camera is exposing the photo too bright or dark, it is likely that the light metering is being fooled by the scene having a large amount of white or black.

The reason that this makes a difference is that most cameras are designed to set the average brightness in the scene to the middle of what the camera can capture. This fact means that if you have a scene with large bright or dark areas the camera will under or over expose the image.

The exposure compensation setting can be found in varying places depending on the camera you are using, but in almost every case it has a square icon, divided in half diagonally with a + on one half and - on the other.

Also I should note that I probably won't make it to weekly with this again just yet, but I will be trying to add to it with some regularity.