Just as the name says and the image shows, this mod focuses on improving the lighting of the game and making it more realistic. This mod of the month for February 2013, created by The Realistic Lighting Team can be downloaded from this page on Skyrim Nexus. Instructions on how to install that mod can be found on the same page.
This mod does not affect the game performance in any way. So you will not notice any decrease in your FPS. There is no reason to not install this mod and it is highly recommended to use this even if you do not have a powerfull gaming computer.
