Application Lifecycle Management
The application lifecycle management in SharePoint 2010 means that both developers and designers can now work across the board when designing and deploying customizations. The WSS Solution Package (WSP), introduced as part of SharePoint 2007, has been extended to include sandboxing and more portable characteristics such as the ability to import WSP files into Visual Studio 2010 from SharePoint Designer 2010.
Another major step forward is enhanced upgrade features, including a visual upgrade from version to version. In other words, when you upgrade from SharePoint 2007 to SharePoint 2010 you have the option to keep the 2007 user interface.
Solutions were introduced in SharePoint Server 2007 ...