These are called "Implied In" prices.
Existing bids and offers in spread contracts are combined with bids and offers in individual futures contracts to create additional liquidity in other futures contracts. These are called "Implied Out" prices.
For market makers, implied prices allow relatively low risk spread contracts to generate liquidity in the underlying contracts. For market takers, implied prices mean more liquidity and better prices, whether trading spreads or the underlying contracts.
 External links
For an FAQ about implieds, click the following CME link
For a presentation explaining the mathematics of how implieds are calculated and derived, click the following link