In the broadest sense, the City Council's job is to decide the big picture questions and set the policy direction for the City. The Charter enumerates as Council's responsibilities, to "enact local legislation, adopt budgets, [and] determine policies...." The City Manager and staff then "execute the laws and administer the government of the City."
To ensure some measure of consistency in its policy direction, City Council has adopted and periodically reviews and updates its Priorities document (available on the City website, under the "Our Government" tab, here). These Council Priorities are not only a statement of our most important areas of focus, they guide the city staff in implementing the policy direction they are given. Nothing is done at random; it all ties back to one or more Priorities.