StL (an abbreviation of "stereolithography") is a file format native to the stereolithography CAD software created by 3D Systems. StL has several backronyms such as "Standard Triangle Language" and "Standard Tessellation Language". This file format is supported by many other software packages; it is widely used for rapid prototyping, 3D printing and computer-aided manufacturing. StL files describe only the surface geometry of a three-dimensional object without any representation of color, texture or other common CAD model attributes. The STL format specifies both ASCII and binary representations. Binary files are more common, since they are more compact. (Source Wikipedia: https://en.wikipedia.org/wiki/STL_%28file_format%29)
CADAM3D allows export in StL format. The user must first choose the file format (Test(ASCII) or binary). Since the StL file allows to include only one solid, the user will have to choose which solid will be exported in the file. Finally, the user can choose to apply a rotation to the solid so that the vertical axis goes from Y to Z. After clicking Ok, the user will be asked to save the file as a file with the extension *.StL.