When a group of workers negotiates with their bosses over issues like salary and working conditions, it's known as collective bargaining. The goal of collective bargaining is to reach an agreement that's acceptable to both sides.
Most collective bargaining happens with the help of a labor union or other organized group representing employees. Typically, the union speaks on behalf of the workers it represents, laying out their requests (like wages, benefits, working hours, and safety, and other issues). Collective bargaining can result in improvements at a single company, but sometimes it leads to better working conditions in an entire industry.