Screenshots would be pretty dull. As Chaos says, it is a board game played on 19x19 square grid. Players alternate placing black and white stones on the intersection points of the grid. To remain alive, a stone most have at least one open space ("liberty") adjacent to it. Stones of the same color which are adjacent along the grid lines are said to be connected and they share their Liberties. When a stone or group of stones loses its last liberty, it is "captured." Keeping stones alive is merely a means. The goal of the game is for your stones to capture territory. If you think about the 'keeping stones alive' rules, it should be abvious that a portion of the board surrounded by one color of stones is 'safe.' When the players feel that there are no more profitable moves to be made, they determine who controls which territory, they count the number of open intersection points in their territory, subtract the number of their stones which have been captured, and that is there score. Functionally, what you do is fill up your opponents territory with your captured stones to make the counting easier.
This game is one of those easy to learn, difficult to master games, like chess only more so. Low level games,like I have played, involve lots of rows of black and white stones next to each other and lots of captures. In high level games, the players rarley actually capture stones because both players know when a stone (or a group) is doomed and they do not need to waste turns by killing it off. Unless the doomed group's side manages to reach out from another part of the board to 'rescue' them, they will be removed as if captured at the end of the game.
The game has its origins in China, but has millenia old roots throughout East Asia. (Currently, the Koreans are generally received as the best players, but the balance of power has shifted over the years among Chine, Japan and Korea. It is kind of like the Rider's Cup in golf.) Only handful of Westerners have ever achieved professional rank as Go players. I will not be one of them, but I like the game just the same...