Mesh files are most commonly used in manufacturing methods such as 3D printing, rapid prototyping and computer aided manufacture.
They can also be used for inspection, measurement and reverse engineering.
A Mesh file can be generated from a point cloud file, created by 3D scanning equipment. This process does requires some post processing of the scan data to optimize it for use with an .stl.
Additional post processing actions can be performed on mesh files too, such as smoothing, de-featuring, filling holes etc.
Mesh files can also be created by converting CAD models,
This allows for the creation of hybrid models, where some features have been created from scan data and some by more conventional CAD.