When an employee group collective withdraws services or engages in some sort of action to disrupt the operation of an employer the catch-all term is job action. One of the most visible forms of job action is a picket line, where employees completely withdraw their labour and typically ask other unions to not cross their picket lines. Less visible types of job action can include over-time bans, where employees refuse to work beyond their scheduled shifts, work-to-rule, where employees perform the duties required of them in their job description, and study sessions, where the workers meet to learn about bargaining, their collective agreement or other issues, rather than going to work. Unions may choose to engage in as many types of job action as they desire.
Job action is always designed to put pressure on an employer in order to reach a collective agreement. Job action is not the goal of any union; it is only a very effective means to achieve the ultimate goal of improving the lives of workers.
You can read a brief synopsis of the TSSU’s 2012 job action here.