I've read several articles in recent months about Chinese naval strategy, referring to "first island chain" and "second island chain".
And believed to be part of their strategy but not fully proven, a "third island chain", a defensive perimiter of islands to protect China from invasion, or alternately, to expand its naval trade interests and shipping lanes.

Here's an article I dug up, with maps, that explains it pretty well:

http://www.globalsecurity.org/military/world/china/plan-doctrine-offshore.htm

The "second chain" extends out to Guam and the Marianna Islands, and south to Australia.

The "third chain" is believed to include Hawaii. China's plan is to "layer" defenses so they can sink any ship, with either Chinese naval power or Chinese missiles out to these island chain regions.