In other words, typical 3D is made of polygons whose vertices are specified to arbitrary precision, whereas voxel-based 3D content is a big three-dimensional array of discrete values. The voxel data can be coarse (like Minecraft) or quite smooth (like an MRI scan), but the distinguishing feature is that the data is discrete.
2D : pixels :: 3D : voxels
but you might find this more intuitive:
typical 3D : vector graphics :: voxels : bitmaps
In other words, typical 3D is made of polygons whose vertices are specified to arbitrary precision, whereas voxel-based 3D content is a big three-dimensional array of discrete values. The voxel data can be coarse (like Minecraft) or quite smooth (like an MRI scan), but the distinguishing feature is that the data is discrete.