Okay, I've had Steam for years and was surprised to note when I just checked that I have 82 games/sims on it in my library. Now, apparently these grant 'Trading Cards' whatever those are, of which I evidently have about 90, granted from various titles in my Steam library. Four of those are from Flight Sim World, which I think were granted because I've done some of the missions in the sim. These trading cards are apparently worth '22 Gems' each (whatever that means), the Gems can also be converted into 'Booster Packs' (again, no idea). So does anyone know what that all means?

Don't know if it helps?

http://steamcommunity.com/tradingcards

I'm still left wondering what to do with them...

Cheers for that. So...

'Once you’ve collected a set of cards you can craft them into a game badge. Like the current badges, they are tied to your account and are shown on your profile. Unlike the current badges, crafting game badges earns you marketable items like emoticons, profile backgrounds, and coupons. Level up your badge by collecting the set again and earning more items.'