A union is an organization formed by workers who join together to have a voice in their workplace and negotiate from a position of strength with employers over wages, benefits, workplace health and safety, job training, and other work-related issues. Unions can organize a particular section of skilled or unskilled workers, a cross-section of workers from various trades, or all workers within a particular industry. The agreements negotiated by a union are binding on the rank-and-file members and the employer, and in some cases on other non-member workers. Unions are democratic organizations, and their leaders are elected by the membership.

Collective bargaining is the process of negotiation between employees and their employer over wages, working conditions, benefits, and other aspects of workers compensation and rights. Unions work to improve the negotiating leverage of their members through collective bargaining. Unions also serve an important role in making sure that management acts fairly and treats its workers with respect.

Unions can provide wage premiums and reduce inequality while reducing employment growth and restricting employment flexibility. Union workers are more likely than their non-union counterparts to have access to health care and pension benefits. Unions can also engage in politics and promote laws and policies on behalf of union members.