A word invented for a play
There were no robots before 1920. There were machines, and there were clockwork figures — an AUTOMATON that poured tea or wrote a letter — but the word itself arrived with a Czech play, Karel Čapek's R.U.R. His brother Josef suggested it, built from robota, an old word for forced labour, and Čapek used it for artificial workers built to do the jobs nobody wanted.
The play ends with the robots rising against the people who made them. So the idea of the machine that turns on its maker is not something Hollywood added later — it was there in the very first story to use the word, a century ago, and it has never really let go.
Sense, think, act
Every robot, from a toy to a factory arm, runs the same three-step loop. A SENSOR gathers information — light, distance, heat, pressure — which is the machine's version of eyes and skin. A PROGRAM on a small CIRCUIT decides what that information means. Then an ACTUATOR does something about it, usually a MOTOR or a SERVO turning GEARS to bend a JOINT.
Remove any one of the three and the whole thing stops being a robot. A MACHINE that senses and thinks but cannot move is a computer; one that moves without sensing is just a MECHANISM running blind. It is the loop, not the METAL, that makes it a robot — which is why a device covered in WIRES and topped with an ANTENNA might not qualify, and a plain box on wheels might.
The hard things are easy and the easy things are hard
Here is the great surprise of robotics. A computer beat the world chess champion in 1997, but building a robot that can walk across a cluttered room and pick a sock off the floor is still genuinely difficult. Researchers call this Moravec's paradox: the skills we think of as clever — arithmetic, logic, chess — turn out to be the easy ones to program, while the things a three-year-old does without thinking are extraordinarily hard.
The reason is that walking, grabbing and balancing were refined over hundreds of millions of years of evolution and run below conscious thought, so they feel effortless to us and look simple. They are not. Every steady step a HUMANOID robot takes is a small engineering triumph, and every time one falls over in a demonstration video, it is failing at something harder than chess.
Most robots look nothing like us
The robots doing real work are mostly one arm bolted to a floor. Unimate, the first industrial robot, started at a General Motors plant in 1961 lifting hot metal castings, and its descendants now do the WELDING and painting on almost every car you see. No face, no legs, no ANDROID or CYBORG about it — just a very repeatable elbow.
Distance changes the design too. A Mars rover cannot be steered like a remote-control car: a radio instruction takes minutes to arrive, so by the time a human saw a rock and reacted, the rover would already have hit it. Instead it is given a destination and left to work out the route itself, checking the ground with its own sensors. Whenever CONTROL cannot be instant, the machine has to be trusted to think — which is also true of a DRONE flying beyond its pilot's sight.