quick noob question

Open box is like a return basically, or they are just needing to get rid of it, or someone's opened it. But probably a return. OEM is Original Equipment Manufacturer, you are still getting a new product, but you don't get all the little niceties, like the extra software or cables, or spare parts, screws etc that you would get with a retail version of the product.

Open box is kind of a touchy subject. It just depends on whether you're willing to risk having to deal with the manufacturer for a replacement instead of newegg, as they will only accept the return for a refund, and only within 15 days..