GIN is "Get It Now". You can it to grab an item immediately without having to go through with the auction or worry about other bidders. GIN closes the auction as soon as you use it.
Here is the info about a fixed price listing or using the GIN feature:
A Fixed Price listing is a type of listing where there is no bidding, and the only way to win it is to use the Get It Now feature.
A seller with the "Seller Wings" badge can list an item with a Fixed Price at the time they create the listing by clicking the Fixed Price tab that's located below the listing's Description.
A value between 2,000 and 5,000,000 credits can be entered. There will be a small listing fee when the item is listed, and a % of the credits earned will be deducted from the total sell price.
The Fine Print: When a Fixed Price item sells, the transaction fee (%) is collected when you receive the credits for your item. The listing fee is collected once a listing goes live and is non-refundable. If a listing with the Fixed Price feature ends without a winner, the listing fee is not refunded. If the listing is automatically re-listed, a new listing fee will be charged each time.