The priority determines the order that jobs run. If another job is scheduled to run at the same time as this job, the priority you set determines which job runs first. The priority is changed for all occurrences of the scheduled job.
The priority of the job is displayed in the Priority column in the Job Monitor on the Job List tab.
If there are multiple backup jobs using the same selection list, then updating the priority of one backup job will cause the priority for the other backup jobs to be changed as well. If this occurs, you are prompted before the priority is changed for all backup jobs that use the same selection list.
You can select multiple jobs by selecting a job, and then pressing the <Ctrl> or <Shift> keys while you click other jobs that you want to select. This allows you to perform tasks such as setting priorities on more than one job at a time, as long as the jobs are of similar type.