In addition to the basic UV Mapping funtions there are some additional functions for mapping surfaces.
Since it is generally undesirable to export every single facet of a surface as an individual 2D part the Surface functions are designed to gather groups of facets to create Segments of the 3D object. The resulting segment can then be converted into editable 2D parts.
The functions and ther purpose are as follows:
Quick Selection: Selects a contiguous series of facets based on the setting in the UV Mapping Options.
Create Segment by Selection: Creates a segment based on the currently selected facets.
Auto Segmentation: Automatically composites a set of segments for all facets of the selected 3D object.
Explode Segements: Explode the currently selected facets back into facets.
Unwrap Segments: Unwrap the selected segments into 2D Parts.