What it says on the tin.
A manufacturer refurbished 15" Retina MacBook Pro. Usually customer returns under 14 days return facility sold in as-new condition with full warranty.
What's not to like? It's the closest you'll get to a discount.
You'll get more for your RRP money after WWDC. If the refurb meets your requirements and it's a good price then buy now while they still have stock.