The Job History page displays a list of runs for scheduled and unscheduled jobs. Click the appropriate tab to see the information and the historical details.
The Scheduled tab shows the jobs that were run on the schedule.
The Not Scheduled tab shows the jobs that were run manually or because of the action processing of a flow.
Schedules require the prior schedule of the same object to finish before a new schedule can start. The new schedule will be either skipped or canceled if the prior schedule is still running. A long running schedule can happen when there are many records being processed for an object.