"Through the green" is a term you hear all the time at the U.S. Open and in big professional golf tournaments, as well championships conducted by the USGA and R&A. However, if you asked 10 golfers, there's a chance half of them wouldn't actually know the space on the golf course considered "through the green." So, let's help them out.
"Through the green" in golf and under the Rules of Golf is the space on the golf course that is everywhere except for the teeing ground, putting surface and hazards, including water hazards and bunkers.
Now, here's an added wrinkle that will come up in 2019, when the new edition of the Rules of Golf is published and takes effect. The term "through the green" will be changed to "general area," but it will still mean the same space on the golf course.