Job plans aggregate work orders that have something in common. Usually that commonality is the period during which the work covered by those work orders is to take place. Perhaps one set of jobs depends on another and it would be beneficial to look at those jobs at a same time to allow for proper planning. Additionally, at the end of the period, there may be some things that were learnt not only on each of the jobs (that will be documented on each work order) but also on the overall collection of works done during that period. Job plans allow for that: you can add general common notes to the group of work orders to refer to at a later stage and you can also look at a Gantt graph that lists all the work orders to perform on that period.
If your plant or facility has regular maintenance overhauls, stoppages, etc you should investigate the power of job plans in comma CMMS.