There are several concepts introduced as part of planned (and unplanned) maintenance. Their definitions are as follows:
A maintenance task is a single maintenance activity carried out by suitable personnel. The maintenance task details instructions on how to perform the task, the expected time it will take to complete the task, and a list of necessary parts required to complete the task.
A maintenance plan is a collection of tasks that are performed on a scheduled basis. The maintenance plan groups several tasks together and defines the frequency at which the tasks should be undertaken.
A maintenance class is the mechanism used to group plans together for assignment to assets/equipment. The class may contain several maintenance plans of different frequencies. Rather than assign many individual plans to many individual assets, the class is used to define the group of plans to be assigned to many assets.
The is the instruction to undertake maintenance activities. A maintenance order can be created automatically as part of the maintenance scheduling (planned maintenance) or can be manually created for an individual asset (unplanned or emergency maintenance). The order contains the list of tasks, instructions, due dates, the people assigned, and the list of parts required