Prophylaxis or Maintenance visits are your regular dental cleanings.  By definition, periodontitis patients have "maintenance" visits, while patients with no history of periodontitis have "prophylaxis" visits.  

While they technically mean different things, each procedure is a simple tooth cleaning that lasts about 45 minutes.  Periodontal maintenance visits focus more on problem areas and areas with residual deep probing depths.  

Patients with a history of periodontitis will typically have maintenance visits every 3-4 months rather than every 6 months with prophylaxis patients.  It takes plaque approximately 3 months to become pathogenic, so a cleaning every 3 months goes a long way to prevent recurrence of disease.  In fact, studies have shown that patients who undergo treatment and adhere to regular maintenance lose about half the teeth patients who undergo treatment but have erratic maintenance.