Collective bargaining is a process of negotiation between employers and a group of employees aimed at agreements to regulate working salaries, working conditions, benefits, and other aspects of workers' compensation and rights for workers. The interests of the employees are commonly presented by representatives of a trade union to which the employees belong. A collective agreement reached by these negotiations functions as a labour contract between an employer and one or more unions, and typically establishes terms regarding wage scales, working hours, training, health and safety, overtime, grievance mechanisms, and rights to participate in workplace or company affairs. Such agreements can also include 'productivity bargaining' in which workers agree to changes to working practices in return for higher pay or greater job security.