Hey now, what’s this? Is Steam going to dip it’s toe into the action of player to player trades? Not so fast there hot shot, this is only for gifts. You can’t go trading your library of games for other games, only unused gift copies of said games are able to be traded. However if you are really itching for some Team Fortress 2 hats or items, you can trade those for gifts as well. This is definitely a step in the right direction, now they just need to let us swap games damn it! Get in on the trading action by selecting the Steam Trading Beta from your Steam settings in the Steam client.
Source Link: Steam Support