Hmm, I was a little confused at first, but then I think I got it. I'll give you my thoughts anyway.
Dale was a city outside Erebor. When Smaug attacked Erebor, Dale was also destroyed. So Dale is in ruin, hasn't been rebuilt because Smaug still inhabits Erebor.
Laketown is similar to Dale, but is poorer. It's further from Ererbor which means it's at less risk from Smaug. The Master of Laketown is mayor while Bard is just a captain.
I'm not entirely sure of these parts, I may be wrong but I'm sure someone will correct me. After the Battle of Five Armies, Dale is rebuilt and ruled by Bard and his descendants. During the Battle for Middle-Earth (Or War of the Ring), Dale is attacked by the Eastern Kingdoms. Drain and the soldiers of Erebor defend Dale. These were not shown in the films due to budget, but it happened in the book. This was to prevent any help from those men or the dwarves when Sauron assaulted Middle-Earth.
That's pretty much all the history I know myself. If you want to learn some more, you could go on Middle-Earth Wikia. They have loads there on anything you could possibly need! It's even an app