What it is:
How it works (Example):
Technically, anyone who buys or shorts a security with the expectation of a favorable price change is a speculator. For example, if a speculator believes XYZ Company stock is overpriced, they may short the stock, wait for the price to fall, and make a profit. It's possible to speculate on virtually every security, though speculation is especially concentrated in the commodities, futures, and derivatives markets.
But to really understand speculation, one must understand how it differs from hedging. Let's consider an example: let's assume part of your investment portfolio includes shares of Company XYZ, which manufactures autos. Because the auto industry is cyclical, Company XYZ shares will probably decline if the economy starts to deteriorate.
If you want to protect this investment -- that is, you want to hedge your investment -- one way to do that is to buy defensive stocks. You may choose "noncyclicals," or companies that sell basic necessities like toothpaste or toilet paper. During economic slumps, these stocks tend to hold or increase their value, which could offset the loss in value of the XYZ shares.
A speculator wouldn't follow this strategy. If a speculator purchased food-company stocks, he would do so because he simply believes the stock is going to increase.
Speculation can increase short-term volatility (and thus, risk). It can inflate prices and lead to bubbles, as was the case in the 2005-2006 real estate market in the United States. Speculators who were betting that home prices would continue to increase purchased houses (often using leverage) intending to "flip" them for a profit. This increased the demand for housing, which raised prices further, eventually taking them beyond the "true value" of the real estate in many markets. The frenzied selling that ensued is typical for speculative markets.
Why it Matters:
Some people may see speculators as dangerous gamblers, but speculators actually provide much-needed liquidity to markets and are thus a vital component of market efficiency. Without them, many commodities markets, for example, would virtually grind to a halt because the only participants would be farmers and food companies. With fewer participants in a market, bid-ask spreads would widen and it would be much harder for buyers and sellers to find each other. The resulting illiquidity would dramatically increase the risk in that market.