The "Archive Course" tool creates a downloadable "permanent record" of a course including all the content and user interactions. When an Archive package is restored, the content of the course AND user data & interactions are restored as well. The course is restored to the state it was in when archived. Archived courses are saved as ".ZIP" files with the following file naming structure: "ArchiveFile_YourCourse_ID.zip".
The "Export Course" function creates a downloadable package of the course content that can later be imported and used to teach another course with the same content. It is important to note that "Export Course" does not include any user interactions with the course -- it only includes content and tools. Export packages are downloaded as compressed ".ZIP" files and are imported in the same format. They are saved with the following file naming structure: "ExportFile_YourCourseID.zip".
Once the Export or Archive package has been downloaded, do NOT remove files from the package or unzip the package and try to restore individual files within the package. Your course can only be restored (in the future) if the zipped package remains intact.
Please check this Knowledgebase article for instructions on how to export/archive your Blackboard course.