What is a grouping?
A grouping is a collection of groups. If you wish to use groups for two distinct purposes within a course (e.g. one set of groups for splitting a forum discussion by topic, and another set of groups for tutors who will mark Assignment submissions) then you need to put the related groups in a grouping. Otherwise Moodle won't know that the "Bob" and "Sue" groups are different from the "Physics" and "Chemistry" groups and will try to use all of them at the same time. See Groupings for an example scenario.
Once you have added groups to a grouping, you can choose a grouping for each group-based activity in its settings and only the groups within that grouping will be used rather than all groups in the course.
Previously, it was only possible to hide an activity from an individual or a group, by using Groupings. Since 2.7 this can be achieved much more easily (and with more flexibility) by using the Conditional Activities settings.
What is the difference between a group and a grouping?
A group is a set of users. A grouping is a set of groups. See the above answer to What is a Grouping? for more info.
- Groups forum in Moodle in English