A mesh is a connected or disconnected collection of vertices and polygon faces that approximates the surface of a 3D object.

Elements
Vertices, edges, faces
Render primitive
Usually triangles
Surface direction
Normals
Texture coordinates
UVs

Quality is contextual

A high triangle count can preserve scan detail but hurt web delivery. A low count can be efficient but lose silhouette detail. Judge density where it affects the intended view.

Generated meshes need a hidden-side review

Inspect the back and underside, then check normals, disconnected shells, thin structures, and intersections before rigging, printing, or simulation.