As if there weren’t enough games to play on Steam already, Steam has gone and tuned itself into its own game by introducing a trading card game mechanic. So join the Steam Trading Cards Community Group page and score yourself a beta invite to Steam’s new meta-game.
The way to play is easy enough. Each of the participating games is associated with a particular set of collectible cards, at least half of those cards can be earned by simply playing one of those games. The rest of the card set requires a certain collection prowess as you trade with fellow community members and friends who might have a card you require. Once you have completed a set of cards, you can craft those cards into badges that will adorn your profile. Best of all, and unlike other community badges, Steam Trading Card badges will net you rewards like emoticons, profile backgrounds and more.
All badges will now also “have XP which contributes to your Steam Level, a summary of your badge collection. You can view someone’s Steam Level by hovering over their avatar. Leveling up earns you non-tradable items like profile showcases, extra friends list slots, and more“
The games that are currently participating in Steam’s Trading Card Game are Portal 2, Don’t Starve, Dota 2, Team Fortress 2, Counter-Strike: Global Offensive and Half-Life 2. The fact that Don’t Starve is included means that other non-Valve titles will probably join the latest card craze soon enough.
Source : Steam Community