Moodle LMS administrators use a very specific set of vocabulary. For example, a "course" in Moodle has only one definition. It is the space on Moodle where teachers add activities and resources for their students. It is important that you also use this vocabulary to prevent mistakes and to streamline communication. For example, if you tell a Moodle administrator to delete a “course” when you actually mean a SCORM package, you will be very unhappy when 100% of your English 101 activities and resources suddenly disappear and your students can no longer find English 101 in their catalog.
Here are the definitions of Cohort and Group and some links where you can find more information.
Cohort- A subset of users at the site or category level. The subset can be based on any profile field. For example, you can have a cohort of accountants, workers in California, trainees in a management program, new hires, people with a shoe size of 8 wide, etc. Any data that you can collect can be used to create a cohort.
The primary purpose of cohorts is to enable all members of the cohort to be easily enrolled in a course. This can be done using Cohort sync, which, as the name suggests, synchronizes cohort membership with course enrolment. Alternatively, a cohort can be manually enrolled in a course.
A secondary use of cohorts is to easily pull reports on specific subsets of users. Students are not aware of the cohorts in which they are members. Cohorts are only visible to users with higher level administrative permissions such as site admins, managers, and teachers. Students can belong to many cohorts at the same time.
This term is commonly confused with group. You can read more about cohorts here: https://docs.moodle.org/401/en/Cohorts
Group- A subset of users at the course level (context). This is used when you have groups of users (perhaps from a different school or company) taking the same course and you want to quickly see completion reports for each of those groups of users, rather than all the users in the course. Groups can also be used when you want a supervisor from the school or company to be able to check on completions for their own users but not be able to see data on other schools or companies. This term is commonly confused with cohort. You can read more about groups here: https://docs.moodle.org/401/en/Groups