@fissaadmin
Batches are a special form of the group. In a course, if the setting is enabled that batch enrollment is necessary then you cannot enroll in the course without enrolling in the batch.
In this way, you can restrict users to enroll in the batch first if they want to access the content of the course.
Linking Course
It's a feature if someone wants to show a page where all the batches visible. To identify which batch is connected with which course this will work for that.
How to admin user to a group
recording:
https://screencast-o-matic.com/watch/cYnuixw9Hz