After learning that go is (mostly) a two player game, where one player uses the black stones and the other player white ones, then you are ready to learn the existence of territory. This is a very important concept because the winner of the game is the person who has managed to surround the most territory. Here are 3 examples of territories:
Here are three examples of how one can close of his territory. A is for the corners, B is for the side and C is for the center. When you want to know how many points each territory is worth you just need to count the intersections that you have been able to surround like so:
In the second figure black has surrounded 9 intersections. At the end of the game this means he will get 9 points for this territory.
To see if you have grasped the concept here are 3 counting problems:
How many points will black get here? (The answers are at the end of the post)
Answers (P1 = 5 points, P2 = 13 points , P3 = 8 Points )
Okay great! ^^ next step is understanding the liberties