What the hell are Steam cards?

S31

I got two Steam Cards in my inventory and I don't know what a hell are they and what should I do with them?

Dirk Gunderson

Screenshot?

S31

Me [AUS]

Where do you see that? In the game or on steam?

[7TW] Attack Eyebrows

These cards are obtained if you play the game through Steam. Some are awarded for simply playing the game, the rest can be obtained by making puchases in-game or through the Steam Community Market. If you collect them all, you can craft a badge on Steam. There are no special benefits other than the satisfaction of having crafted the badge and being able to show it off on Steam.

You can of course also sell the cards on the Steam Community Market; gets you back a few cents (literally) from your purchase (and Valve will collect about $0.02 per transaction). How's that for money grabbing, $0.02 fee on a $0.05 transaction, netting you $0.03?