MESH/SOLID ANATOMY FAQ
Q: What are "meshes" anyway ?
A: meshes are polygon faces, basically triangles,
and many of them form the wall of a 3d geometry
like a mesh - this is the most convenient form of using
3d data, they have been used since decades for animation
and illustration, and movies like "Ice Age"."
Pretty compatible and with a plethora of software
(you can even download good 3d mesh programs free),
one can do all sorts of things with meshes,
that you cannot do with NURBS.

Q: Why then do CAD programs use "NURBS" instead
("non-uniform rational b-splines") ?
A: Good question - NURBS are mathematical descriptions
of what meshes actually show, and as such they are
more easily susceptible to mathematical tricks than meshes,
which behave more the analogous way - therefore,
NURBS are really useful in scientific software,
fluid analysis an the likes, and, though rarely,
in normal construction. However about 12 years ago
there was a "Nurbs fad", and many people cried
"just say no to polygons !", thinking
the then new-fangled NURBS would solve all.

Not so - nowadays we have the unfunny situation
that mesh animation software uses NURBS internally
(only where they are convenient to use) and meshes
elsewhere, while CAD programs are practically
restricted to NURBS and cannot handle polygons -
there are rare exceptions (Rhino 3D.
or format STL which is frequently used
for Virtual Prototyping.
Funnily VP mostly calls for a mesh solid,
which works just fine tough many people
will not even believe it exists.

"So I turn mesh objects into NURBS solids myself with expensive software like Rapidform, Geomagics..."
Oh sure, try it...
You just may not like the results.