I read through the lesson and the quiz. Words do seem to be used interchangeably w/o saying that out loud. I'll see if I can get an update.

All optional actions are optional user actions because a user has to make a purposeful choice to take one of the available actions.

Optional (user) actions come in two flavors:

1) a local action - which is always ever just a single assignment, and

2) a process - which can include more than one assignment - and a bunch of other process related steps.

The key data point about a local action is that, while I am actively working an assignment, I can do something else in a single, but different assignment - then come back to the original assignment and finish it. This is the primary reason a local action is sometimes referred to as an optional user action; because it cannot be completed w/o user intervention (action). Not the best choice of words, but that is the connection most folks make.

The key data point about an optional process is that, while I am actively working an assignment, I can kick off an entire separate process - which may contain automated steps such as sending an email, evaluating a decision table, changing from one stage to another, even closing the case. Because these automated steps do not require user intervention, these are commonly referred to as optional processes. An optional process can most certainly be completed w/o user intervention; except for invoking it in the first place of course. 

does this help clarify?

eddie