That's another different thing too , I will clarify more (and tell me which one you need , if it's a gift for a game I can sell you that) :

• Steam gift card code : It's steam wallet which gives you basically money into your Steam account comes with different values (10$ , 20$ etc ... ) and can be used to buy from community market (Dota 2 , CS:GO items etc .. )  or buy games from Steam it self .
• Steam Gift : Basically specific game you can buy however instead of buying for your self you buy it as giftable on your inventory so you gift it to someone later or use it for your self if you don't have it (can be sent by email , trade or to steam account)
• Steam key : Just like Steam gift however it's just a  key and it's redemable on steam for a specific game (once it's redeemed you can't give it)