You watch a movie and there is something off putting putting about a scene. You end up not liking it. However, at a much later time, it finally hits you. You finally understand what that scene or thing said during it meant! It is basically an epiphany and you may now like it because you figured it out. This is Fridge Brilliance in a nutshell.
Have you ever come across that in your own movie going experience where you don't seem to understand what that scene means, but then you realize the truth and suddenly that stupid moment makes total sense now? An example for me is when I watched the live adaption of Animal Farm where the reign of Napoloen finally ends and new owners come to take over the farm. Upon realizing it, the film was made after the fall of the Soviet Union and that collaspe of pig's rule was an allusion to end of the old government in the SU. The new owners were an allusion to the new government and the final words about whether or not the new owners will be good or not is how people may have felt after the new government came into power in Russia. It makes sense! I brought that explaination to the my English teacher, who showed the movie, was shocked by the realization.
Anyways, here's a site that shows what people thought was fridge brilliance in movies. I like some of their thoughts on the Star Wars prequels, which kind of make sense if you think about it:
http://tvtropes.org/pmwiki/pmwiki.php/Fridge/Film (http://tvtropes.org/pmwiki/pmwiki.php/Fridge/Film)