They are two major types of representative bodies that can legally support employees, which are the trade unions and non-trade unions.
Trade unions are big organisations specialised in a certain occupation and/or common type of industry which employees are associated members of the union. They can help and advice employees to (and) moderate points of legislation, such as health and safety, data protection, pensions, work redundancy etc., which can affect workers in a business environment.
Trade unions can assist their members through work-based representatives as well as regional and national experts.
Examples of non-trade unions includes staff associations and trade associations, which can also be found in organisations.
Non-trade unions are limited in regards aiding employees with their legal questions as their role is a lot more restricted and mainly focused to provide consultation.
The biggest difference between trade unions and non-traded unions is that the last one does not provide provides legal advice for Union learning and Collective bargaining.
However, the common point between them is they may share a consultative forum within the same company.