According to Wikipedia, a voxel (or volumetric pixel) “represents a value on a regular grid in three-dimensional space”. In the context of RPG in a Box, voxels are the building blocks (think 1×1 LEGO bricks) used in the creation of your game's tiles, objects, and characters. Each voxel is visually represented in the Voxel Editor as a cube and possesses a unique XYZ coordinate within the editor's three-dimensional grid.
Whenever a tile, object, or character is saved in the Voxel Editor, an optimized mesh and corresponding texture is generated using the voxel data (i.e. voxel coordinates and colors) for each frame. Although each resulting model is no longer composed of the individual cubes in-game, this information is stored as metadata on the entity for future functionality.