Operation manual is a technical writing deliverable that instructs the end-user on the documented product: what is it, what is its purpose, how to use it safely and how to troubleshoot problems.
It is a kind of deliverable that goes, for example, with any piece of technology. Imagine that you’ve bought a new printer. When you do the unpacking, there’s always a user manual included in the package. In case of a printer, from the operational manual you may find the description of the product and its functionality, learn how to maintain it, how to connect it to your PC and so on.