The definition in CATIA v4 documentation is: "most useful to "simplify" a skin, that is deform a reference surface so that it matches as closely as possible the initial skin, while taking a number of parameters into account (draft direction, curvature value, tolerances, surface stretching and bending)".
This short paragraph (which is in fact the beginning of the explanation of this command) is from CATIA v4 CD documentation at the end of FORMTOOL FUNCTION chapter - page 36 (in CATIA Advanced Surface Design - Interactive Function Reference Manual).
Hope this will help you to find more details about that.