This article explains how to trade Steam games under certain circumstances. You cannot trade games from your library, only those in your inventory. You can also trade various items in your inventory for games if you can convince your friends to make the deal.

If you have a tradeable game in your Steam inventory, you can trade it just like you would Steam Cards, in-game items, and other things in your Steam inventory.

Here's how to trade Steam games:

In the Steam client, select your username at the top and choose Inventory from the drop-down menu.