Machines can precisely repeat predetermined motions. Robots can do that too, but they can do even more.
Robots can be programmed (given instructions) to perform many tasks. So, even when the task they have to do changes, we do not have to change the robot. Just by giving the robot different instructions, we can tell it to perform different tasks. This means that even when the robot has to install different parts on different cars, it receives the appropriate instructions and installs the corresponding parts correctly. A robot can precisely repeat the task written in its instructions while moving smoothly like a human arm. Machines and robots are used in many places inside our factories.