Unsettled - Introductory
Sometimes stones will be Alive or Dead based on who plays first. Such stones are called unsettled. Look at this shape:
This is the simplest unsettled shape, called the straight three. If black plays here first, the white stones will die.
This makes one large eye, not enough for white to live.
If white doesn't want to play inside, black can play inside. White can capture the two inside stones:
This shape is dead. It's discussed in Dead - Introductory.
So we come to the conclusion that this shape is dead after black plays here first. But what about when white plays?
For the same reason, the bent three is also unsettled: The vital point is at a. Try to see why.
There are other candidates for the simplest unsettled shape: