What are the differences between extending a web app and adding a host header then adding alternate access mappings in SharePoint 2010? My understanding is that , if you are using different authentication scheme for different zones , then extending a web app. If you would like to access the same web apps but with different URL for different zones ,using adding a host header then adding alternate access mappings. Please feel free to correct me if I got it complete wrong.
Extending the application allows you to view over a number of different hosts (using AAM) but more importantly allows you to specify a different authentication provider and security settings.