A robot is a virtual or mechanical artificial agent. In practice, it is usually an electro-mechanical system which, by its appearance or movements, conveys a sense that it has intent or agency of its own. There is no consensus on which machines qualify as robots, but there is general agreement among experts and the public that robots tend to do some or all of the following: move around, operate a mechanical limb, sense and manipulate their environment, and exhibit intelligent behavior, especially behavior which mimics humans or other animals. Today, commercial and industrial robots are in widespread use performing jobs more cheaply or with greater accuracy and reliability than humans. They are also employed for jobs which are too dirty, dangerous or dull to be suitable for humans. Robots are widely used in manufacturing, assembly and packing, transport, earth and space exploration, surgery, weaponry, laboratory research, and mass production of consumer and industrial goods. Robotic surgery is the use of robots in performing surgery. Three major advances aided by surgical robots have been remote surgery, minimally invasive surgery and unmanned surgery. There are three different kinds of robotic surgery systems: supervisory-controlled systems, telesurgical systems and shared-control systems. The main difference between each system is how involved a human surgeon must be when performing a surgical procedure. The military is responsible for many of the advances in robotic surgery. That's because military officials hoped that robotic surgery would provide a way for doctors to help patients on the front lines of combat zones without putting themselves in danger. So far, latency issues make long-distance telesurgery difficult, but civilian doctors have put the technology to good use.