In Kohana (with Minion), actions and tasks are sort of similar. Both should be ‘thin’ and do nothing more than create objects of the domain model, and direct bits of those objects to various systems of output. Keeping them both in my mind today is helping me divorce the domain model’s interface from the usual web-based interaction: if I imagine that I’ve got to do the same things in both a web-based action, and a terminal-based task, then they seem to end up thinner.
Testing comes into it as well: the test method (I mean the do_a_thing_test() method, not the method-of-testing) is again similar to the actions and tasks. It mustn’t know much or do much. It only differs in that, in place of setting up some sort of output, it makes assertions about the domain objects.