From ErfWiki

Proposed Canon

The geography of Erfworld is divided into a hexagonal grid.^Erf-b1-p046a Each hex has an associated x,y coordinate system.^Erf-b1-p010 Units are not permitted to cross hex boundaries except when on Turn.^Erf-b1-p115

For more information on hexes and how they are used, see Movement.

Speculation