Jackie, far as I know, they're just trade jargon.

I worked in futures markets for many years. I won't post an entire tutorial here, but just to clear it up a little (and I love the word contango -- I used to run around the newsroom singing "It takes two to contango!" till they finally led me away with the promise of kindness of strangers). But I digress.

You're right, the spot market is for immediate delivery, and it exists for every commodity (though I doubt many pork-bellies investors would like to see a load of such dumped on their office floors). Futures/forward-price markets were originally created to protect farmers, but now mostly attract speculators, who bet on the rise/fall of gold/wheat/currency/crude oil over a given period.