what's the difference between spin.exe and spout.exe

As the rwhitepaper advanced migration scenarios says:

"The two document library migration tools developed by Microsoft are Spout.exe and Spin.exe. Spout.exe, the Document Library Export Tool, is a Microsoft Windows program that reads Web Storage System–based document libraries and exports (or outputs) the selected content as a collection of files in a format that is understood by the import program. Spin.exe, the Document Library Import Tool, is a Windows command-line program that reads the collection of files created by Spout.exe and adds the documents and associated descriptive information to the selected portal area, portal site, team site, or personal Web site on the server running SharePoint Portal Server 2003"