An automated worker was a type of robot employed by a civilization to perform labor in place of its organic citizens. This could free species from unwanted tasks in a free society, or replace the need for their compliance in the case of a tyranny. Often these tasks were ones of a repetitive or dangerous nature.
They appear to have been employed in the societies of Earth and the United Federation of Planets. They were however not ubiquitous enough to be seen in all walks of life, only performing emergency tasks, or being used in hidden capacity as industrial tools.
In the Federation, some androids were considered legally sentient, and thus could not be used as a laborer without their individual consent, an example being the Soong-type android known as Data. During a trial conducted on Starbase 173 in 2365, he was found to have the right to refuse Dr. Bruce Maddox's research. (TNG episode: "The Measure of a Man")
An early example of a successful automated worker was the Dunkleburger Mark XII, a small robot drone which served as a cargo carrier, allowing small manufacturers to compete against larger corporations. They were often treated like pets and given affectionate names. An example of one was kept as the Smithsonian Annex on Nova Atar III. (TOS video game: Judgment Rites)
During Earth's Third World War, android impostors were used for assassinations, and further research was banned following this conflict. This may explain why it took centuries before scientists like Noonian Soong to develop androids as sophisticated as Data. (TNG novel: The Buried Age)
By the 2240s, at least some police duties on Earth were conducted by primitive androids which were presumably not complex enough to be regarded as a sentient form of artificial life. One such officer arrested a young James Kirk in the Kelvin timeline. (TOS movie & novelization: Star Trek)
By 2385, the United Federation of Planets employed the A500 android synth in industrial labor, such as at the Utopia Planitia colony on Mars. Following a violent uprising, androids were banned throughout the Federation, although it was unclear whether more primitive robots and drones were also outlawed. (PIC episode: "Remembrance")