Surface normals are vectors that are perpendicular to the "faces" on your model.
http://en.wikipedia.org/wiki/Surface_normal
Basically, they point to the "outside" of your model. Some of yours are pointing inward.
(You can tell because they're rendered black in Meshlab.)
You ought to be able to reverse the direction of those normals using your modeling software.
For example, my software (Silo 3D) has an option to select faces and then "Reverse Normals" or just "Unify Normals" to get them all pointing outward (or inward).
I imagine there might be a way to fix them using Meshlab, but I don't know how. Anybody know?
I do know that Meshlab's "Show Normals" option is a little confusing because it shows vertex normals instead of face normals. Vertex normals are basically an average of surrounding face normals.