GIN is Get It Now it's just a option that some sellers put. Like take this auction for instance, you could have put a Get IT Now price of 25,000. So that way a person doesn't have to wait through the bidding portion of the auction and they can just press GET IT NOW and boom you've got your 25,000 that you were asking for.
Also if you become a verified seller, more bidders will bid on your auctions. It just shows that your more trustworthy, not that i'm saying your not. Just a helpful hint. : )