Maintenance is typically considered in Failure, Preventive and Predictive Maintenance. I have added some to this list called Corrective and Pro-Active Maintenance.
FAILURE (or REACTIVE) MAINTENANCE Also called "Fire Fighting". BUT realise sometimes a strategy of "Failure Maintenance can be chosen on purpose when a functional failure does not jeopardise any safety, environment, customer impact or cost effect. E.g. an asset that is purely supportive and can be repaired without production or cost impact could be treated with FM strategy.
CORRECTIVE MAINTENANCE Sometimes confused with failure maintenance, however true corrective is a task that follows as a corrective action after a predictive inspection showed there is an expected or non-urgent action required. In other words this is the follow-up work after a PdM inspection.
PREVENTIVE MAINTENANCE Replacement of adjustment "In Time" or Meter Based", typical are: calibration of instruments, lubrication/greasing tasks or hourly based component replacements. In general this tasks means replacing parts "in kind". The downside of PM is there is no indication when the part is really worn, so in general, to be on the safe side this is done on a shorter interval than possibly technically required.
PREDICTIVE MAINTENANCE Inspections that show magnitude of wear or degradation. Typically this does not mean changing parts but rather give information about the state of the asset. Examples are: Thermography, Vibration, Ultrasound, Oil analysis, Current Motor Testing.Incase anomalies are found this will be reported incl possible urgency and corrections or repairs are called CM, Corrective Maintenance.
PRO-ACTIVE MAINTENANCE To avoid functional failures at all. Is more involvement in the early stages of asset design and installation, involvement in changes of process and assets and implementing new (more reliable) techniques. Asset history and awareness is most crucial in this process. Need to learn from the past, possible include industry, vendor or other experts information.