No, it's not a dance craze. Contago is a condition of supply and demand, essentially a fancy word to say that prices for items, typically commodities, are cheaper now than they would be at some point down the line.

Anything that¿s sold in the futures market can be in a case of contango. Futures are exactly that: a contract to buy an item or asset at a price in the future. This is the case with oil, with traders buying and selling contracts to acquire a barrel of oil in months down the line. When a market is in contango, spot prices, or the price of a commodity if you were to buy it right now, are lower than forward prices.

Why is that important? Well, it usually tells you the supply of a given commodity is plentiful (since, according to Economics 101, a large supply usually leads to cheap prices).

Incidentally, if you think contango is a mouthful, its opposite condition is known by the equally tongue-tying term backwardation.