Just finished watching it. It was great. But I still have to say...What was going on?

I was confused about what it was exactly that was trying to be put across. The frogs was exodus (the words were right there on a building). But how does that fit in? Were all the stories about something different? Or did they all have one theme to it all? Regret, forgivness? something...
Anyone want to explain?
I still really enjoyed the movie.