Windows SharePoint Services 3.0 includes a new method of deploying custom code and functionality to SharePoint sites that acts as the internal installer framework for Windows SharePoint Services. A Windows SharePoint Services solution package (*.wsp) is a CAB file that includes all custom code and files that should be deployed to a SharePoint site.
Warning: MSDN Archived
When Microsoft retired their MSDN site, it impacted their Visual How To series. Therefore, you may see rendering issues for these Visual HowTo’s including playback problems with the videos. Unfortunately this is out of my control.