Space

Space represents the physical space in-game that could be occupied by units, structures, and obstacles. Typically, only a limited amount of elements could occupy a single space. Some spaces are discrete tessellating cells with regular dimensions or it could be free-form areas. Depending on the format, a space could be occupied by only one or multiple units.

Units typically could only move from their position to an adjacent unoccupied space. If there is no adjacent unoccupied space and the unit is not an air unit and has no special mobility options, that unit may be trapped.

Terrain
Spaces have an intrinsic property called terrain that dictates which units could occupy it or could structures be built there. Most terrain effects are ignored by air units.

Buildable vs Non-Buildable
Some spaces have terrain that's declared non-buildable. Worker units could not build structures on non-buildable spaces.

Obstructed vs Unobstructed
Usually, mobile ground units could only traverse unobstructed spaces. If a space is obstructed (e.g. by an obstacle, structure, or another unit. Obstructed spaces occupied by immovable structures and obstacles are usually counted as non-buildable.

Effect Terrain
Some spaces have terrain that deal indiscriminate damage or give status effects to all ground units that occupy it. Some units with special characteristics (e.g. Mechanical, Undead, etc) may be unaffected by certain terrain effects. Some terrain effects may affect even air units.

Level
Level describes the physical height of a space compared to other spaces. Units could usually only extend their vision to spaces at a level less than or equal to the space they occupy. Air units are usually assumed to occupy the highest level.