Light clipping boxes and areas are used for the implementation of deferred light clipping in CryENGINE. It is a tool that will enable interior spaces to be lit far better and more accurately than they had been in previous iterations of the CryENGINE.
Using light boxes and light areas is highly dependent on the situation. In this example, you should have already completed the prior recipe on Optimizing the levels with VisAreas and portals.
Let's test the process of using a light box: