The term "collective bargaining" was first used in 1891, it is the process were the union employees go through a collective bargaining with the union leaders to set terms and conditions, like for example, they negotiate the payment, benefits, job flexibility, training, etc.
Before the collective bargaining the workers were at the mercy of their employers, they had the power to make all decisions regarding the employee’s work; they chose whatever was cheaper and had no concern about safety or workers’ rights. Until the National Labor Relations Act of 1935 in the US, that made it illegal for any employer to deny union rights to an employee. It also made it illegal for employers to discriminate, spy on, and harass their workers.
Now the collective bargaining process allows them to make a compromise that takes both issues into consideration (employer and workers’ rights) and now is considered to be a fundamental human right.