SHOOT: Backwardation indicates a product is in short supply. In this case, gasoline.
WIKI: A backwardation starts when the difference between the future price and the cash price is less than the cost of carry, or when there can be no delivery arbitrage because the asset is not currently available for purchase.
The opposite market condition to backwardation is known as contango, in which the spot price is lower than the futures price.
As can be seen gasoline is now severely backwardated at the front-end of the curve, while heating oil futures (aka distillate) are still firmly holding on to contango. The flip into backwardation for gasoline happened earlier this month, coinciding with the rampant ascent in the price of US RBOB gasoline futures, which last week hit six-month highs of $1.70 a gallon.