Operations are a code and a name that you can assign to a production step. When you are designing your route data in AX you can use operations and relationships to help with data maintenance.
Using the relationships you can assign resource information and other attributes for the route step. If that one operation is used in many routes then you only need to define it one and you can relate it to many routes. Once this is done if you change that operation relation then all the related routes will be updated.
It does take a bit of planning to use this concept but if you can, it will help you minimize the amount of data you need to manage in AX. This works well where you might have a lot of different routes to make different finished products but a particular step is common between the routes.
Here is a quick overview.
AX2012 R3 CU11