A robot (""worker"" in Czech) can look human or mechanical, but must be capable of some level of autonomous action; otherwise it is just a machine controlled directly by humans. It can do real work--welding cars, inspecting power lines, exploring the surface of the moon--or be merely an elaborate toy. Even with the power of present. day computers to control their actions, robots don't think; but they can choose among alternatives. There is no consensus on whether they will ever equal--or rival--humans. The strength of this overview is the many color photos, showing a wide assortment of these mechanical creatures. Although some science and technology is mentioned, the book is basically nontechnical (and some of the technical descriptions are so terse that they're bewildering: ""Units of electricity are so much smaller than units of compressed air [that] electrical power can be measured out with more exact control""). Still, Skurzynski has done a lot of reading and interviewing, and the result will intrigue many young readers. Chronology; index.