Editing a Package
Editing a package allows you to update the artifacts in the package or add new artifacts to it. When editing a package, you only need to select the artifacts that have changed. For example, if columns are added to a SharePoint list or library and the SmartObjects and forms in the application are regenerated, customized or modified, you can select these while the editing the package and they are updated in the package.
At deployment time, you can select to deploy only the updated artifacts.
See Creating a Package for more information on the options available when editing a package.