The job group gives you the opportunity to create other groupings of jobs than the grouping already made based on the component.
An example could be if a break is planned on the assembly line to carry out different maintenance jobs. A job group can be created for this purpose. The job group will be attached to the jobs that has to be carried out during the break on the assembly line.
When the job group is attached to the job, a search filter can be created for the job group in the job list, just like a search filter can created for resources. Read more here.
Other examples of groupings of jobs through job groups can be a statutory inspection or environmental considerations.
The job group can also be used as a clear division between maintenance jobs and repair jobs.
In most cases, these jobs can be divided by looking at the trigger type (run once jobs or returning jobs), but since you can also create a planned maintenance job that is only to be carried out once, it makes sense to add a job group.
The job group can, just like the resource, be set to mandatory.