What does it mean by unmanned space missions?

The unmanned space missions are those using the remote-controlled spacecraft. The first such mission was the Sputnik I mission, began on October 4, 1957. Few missions are more appropriate for unmanned missions rather than manned space missions, as a result of lower cost and lower risk factors. Because the early 1970s, most unmanned space missions have been based on space probes with the built-in mission computers, and as such possibly will be classified as embedded systems.