Forward and futures markets are an important source of information about prices. Futures markets, in particular, are considered a primary means for determining the spot price of an asset. This should seem unusual, since a spot market for the asset must exist.
Futures and forward prices also contain information about what people expect future spot prices to be. In almost all the cases, the futures market for assets is more deep (volume) and hence, information taken from it is often considered more reliable than spot market information.
While a futures or a forward price should not necessarily be treated as an expected future spot price, a futures or forward price does reflect a price that a market participant could lock in today in lien of accepting the uncertainty of the future spot price.
As on maturity, futures and spot prices must converge, it is said that derivatives markets acts as price discovery mechanism.
Options markets do not directly provide forecasts of future spot prices, they do, however, provide valuable information about the volatility and, hence, the risk of the underlying spot asset.