A crowd of people in front of corporate premises.

A trade union is a membership-based organisation and its membership must be made up mainly of workers. 

One of a trade union's main aims is to protect and advance the interests of its members in the workplace. 

On behalf of its members, unions can negotiate things like better pay and working conditions, provide training for new skills and give general advice and support. 

The law gives you the right to join a trade union wherever you work.