To be patentable, an invention must satisfy two key requirements, as determined by the U.S. Patent and Trademark Office (PTO).  First, the invention must be novel.  This means that the same invention cannot have been disclosed in a single prior art reference.  The prior art is all of the publicly available information that existed before the date the patent application was filed.  Second, the invention must not have been obvious to a (hypothetical) person skilled in the art (the field of the invention) based on the prior art.