Skyrim Digital Download Price Comparison
A Steam gift is a one-time transfer you receive. You activate and install the game on Steam, it is a non-refundable game that stays in your Steam games collection.
For Steam Platform: Steam CD Key (Region Free / Worldwide), you must download and register the code on the Steam Client, you can Download it (HERE). Then once you login, click Add a Game (located in the bottom Left corner) -> Activate a Product on Steam. There type in your CD Key and the game will be activated and added to your Steam account game library.