Layman term explanation of the difference between voxel and point cloud
A point cloud is often derived by sampling.  Each point represents an observation.  Sometimes, a point cloud is turned into a surface by fitting triangles to the points in the form of an STL file.

A raster is a 2D grid of pixels.  It divides the area of an image into constant-sized little squares.  Each of these squares has a value.

A 3D raster is made of voxels.  It divides 3-space into constant-sized little cubes.  Each of these cubes has a value.

Pixels and voxels are rendering techniques.  A point cloud is a sampling technique.

The Wikipedia article, https://en.wikipedia.org/wiki/Voxel, is helpful.

In a real system the pixels may not be square or the voxels not strictly cubic, but in every system I've worked with, they do form a regular tiling of the plane for pixels, and fill 3d space for voxels.