What are main two purposes for labor union

The main purpose is to give workers power to negotiate more favorable working conditions through collective bargaining.

Explanation:

A labor union is an organization of workers joined to protect their common interests and improve their working conditions. It serves as an intermediary between the employer and the employees

Answer: The main purpose of labor unions is to represent the overall interests of the workers and serve as a middleman of sorts between the employee and employer in salary negotiations. The idea here is that an organization of some size is needed to negotiate on equal terms with a big company.