To buy things on Craigslist, then resell them for a profit.
The purchase of items in one market for immediate resale on another market in order to profit from a price discrepancy.
I wasted much of my time playing World of Warcraft, I liked to slay dragons and fight zombies as much as the next guy. But what I really enjoyed was shopping at the in-game auction house. When you had stuff you didn't want, you could sell it to other players through auctions. I was practicing Craigslist arbitrage. And soon my lowly little wizard had a fortune of hundreds of gold pieces.