When you create a group, you are essentially creating a classroom for your students. You can post content, announcements and follow the progress of your students on the lessons you've assigned.
At the start of the year, you may want to build one section of your course and make a clone. A clone will maintain all the content and settings for a group. This way you build one section and make copies with new codes for each section of students.
At the end of the year, you can preserve your course for the students by making a copy for next year and "freezing" the current course. By resetting the group wall and adding content to "no" in the settings, you essentially allow students to access all course materials for reference but no activity can be recorded.
Find more information about how to create and use groups HERE.