Most users of commodities are happy to purchase them via a futures contract. "I'll buy 10,000 tons of wheat at $XX a ton, to be delivered in 90 days." If he and a seller agree on $xx then the buyer waits 90 days and takes delivery on the specified date.
But, what if the buyer has some reasonable doubt that the wheat he can purchase in that futures contract will actually be "there" to be delivered?
Well, to be Really Safe he might insist on taking delivery of the wheat 90 days before he needs it, storing it himself, just to be certain that he has it available for making bread, crackers, and flour.
And, if a lot of buyers are making that kind of demand, then the price per ton of wheat delivered TODAY goes higher than the price of wheat delivered 90 days from now. Like anything else in a market, increasing demand is always reflected in icreases in price.
This condition is called "backwardation" (yeah, I think it's a clumsy term too), because it names a market condition that is "backward" (so far as pricing is concerned) from what you'd find in markets that are not impacted by doubts concerning the availability of a commodity in the future.
In ordinary conditions, a futures contract for wheat will be somewhat higher in cost, because the seller will incur "management costs" (acquiring the commodity himself if he doesn't already have it; storing it; transporting it from where he got it to where he has to deliver it; etc.), and the seller will want to pass those management costs along to the purchaser of a futures contract. And, so, the price of wheat for delivery TODAY is ordinarily going to be lower than the price of wheat delivered in 90 days.
Unless, that is, the buyers of wheat are worried that the sellers of wheat 90 days from now won't be able to fulfill those contracts. In that case, the demand for wheat delivered TODAY increases, and when it increases so much that the price is higher than wheat delivered 90 days from now -- well, then the prices are "backward" from what they normally are. Hence, the term "backwardation."