I don't think there is one. Simply but probably poorly put, supersymmetry postulates that each particle that we know of and have observed has a heavier 'super-symmetric' partner particle. The significance of this is that if true it explains a whole bunch of how the observed Universe works. If it is not true it's almost as exciting really, at least to me, because it means there are some big missing pieces to our current models and a lot of new and exciting work will need to be done.
The short version of the article is that the LHC should have detected supersymmetric particles by now. There's still a slight chance that the next run will, but the energies that fit the current theories are running out. If they are not detected soon physicists might just have to move on to new theoretical models. For one thing, string theory will probably need to be scrapped.