Voxelization is the conversion of mesh objects from their continuous geometric representation into a set of voxels. In essence an input mesh becomes the primary surface of the density function which then can be modified further.

An example of voxelization is shown below:

Applying modifiers to a voxelized mesh:

References

http://www.cs.sunysb.edu/~vislab/projects/volume/Papers/Voxel/index.html