, I'll give you a BioShock Infinite for a Football Manager. Deal? PM me your Steam info and I'll send you mine and I should be around tonight to do the trade.
As for how the Steam "metagame" works:
It's based around two main things: cards and experience (XP). You normally earn cards by playing games that support them. You can find out which games you have that support cards by going to the "Badges" page of your profile. You earn cards simply by playing the games. You will drop up to half the number of total cards (rounded up) available for the game. For instance, if a game has 9 cards, then playing the game will drop 5. All drops happen within 2 hours of play time, though play time prior to the card rollout doesn't count. Some people have simply opened up several games at once and left them to run in order to drop the cards. You may get duplicates. You may get more valuable foil cards. You have no control over this.
Obviously, you cannot collect all the cards for a game by simply playing it, since the drops are limited. Instead, you have to trade with others or buy from the Marketplace. You can also get booster packs. These come to you at random based on your level. Your level is based on your XP. XP comes from how many games you have, how much community participation you've done, and how many badges you have crafted. Apart from the community badge, all other badges are crafted by collecting a complete set of cards, either for an individual game or for the Summer Sale. You can increase a badge's level (which makes it worth more XP) by crafting it multiple times, up to a maximum of 5. This requires, of course, gathering the full set again, through trading, Marketplace purchases, and/or booster packs.
Earning more XP unlocks additional profile benefits, such as allowing you to have a bigger friend list, and setting a background image for your profile page, along with other benefits I'm not familiar with just yet.
I guess this is Steam's attempt at a platform differentiation strategy. Although I think some aspects of it are neat, like the profile customization, I wouldn't be bothered if it all went away tomorrow. Still, my plan is to craft one game badge to complete my community badge, then sell all the others to buy more games. I got a foil card out of Universe Sandbox that's worth like $4.