A while back Greece had a problem. The problem was that it wanted to borrow more money, but didn't want to increase its debt. (Because the European Union would frown on it having more debt.) So it went to Goldman Sachs, and Goldman told Greece, well, what you can do is borrow some money from us, but we won't call it debt, because something something something something swaps.
When you think of Hugo Chavez, you really have to think of the price of oil because oil put him in power and kept him there. Chavez was swept into power because, among other reasons, the low cost of oil.