This is the Sea of Okhotsk:
The story ran in wednesday's edition of the Asia Times, sourced in a report by the Jamestown Foundation (an American thinktank)
As you see from the image published with the report its covered in ice for much of the year.
The Russian win was based on evidence provided that the continental shelf extended over that area.
The area has extremely rich fishing grounds and the win enabled Russia to immediately exclude foreign fishing trawlers. It also igves Russia control over seabed mining rights.
This win also (IMO) gives Russia another reason never to allow the return of Sakhalin to Japan. (Japan wrested it from Russia in the Russo-Japanese war of 1904-5) Russia took it back from Japan in the lightning war in the last 10 days of 1945, and in my opinion (and others) it was the fact that Rusia could easily, at that point, have invaded the northern Japanese island of Hokkaido. Then the mian islands would have been in sight. The Japanese government had to decide whether to surrender immediately to the Americans, or face a Russian invasion.
There are some other implications in this decision made under the United Nations Convention on the Law of the Sea.