What is a swap?

1. The CBOE Web site quotes the CEO of an investment advisory firm as saying: “The VIX Index is an important and popular tool for measuring investor sentiment. . . .” Briefly explain in what sense the VIX is a measure of investor sentiment.
2. What is a swap? In what ways is it different from a futures contract?
3. What is an interest-rate swap? What purpose does it serve?