Edge of the board
In go terms the edge of the board means
- the first line
or more vaguely, referring to an extended area
- the first few lines counting in from the first line.
The tactics of the game are different near the edge, and in particular in the corners near two edges. In general and speaking loosely, the board divides into edge areas and the centre.
It of course never means the actual edge of the wooden board. The area left between the first line and the actual edge should be wide enough so that a stone can comfortably sit, centred on the first line, and not be in danger of falling off.