The end effector is the device at the end of a robotic arm designed to interact with the environment. It forms the last link of a serial manipulator — the point where tools are attached to perform the actual work. In the international standard ISO 8373:2021 (Robotics — Vocabulary, clause 4.12) the end effector is defined as a "device specifically designed for attachment to the mechanical interface to enable the robot to perform its task", with grippers, welding guns and spray guns given as examples.
The form of the end effector depends entirely on the intended application. Common types are grippers (mechanical, pneumatic or vacuum) for picking up objects, as well as process tools such as welding guns, screwdriving or drilling spindles, paint nozzles or measurement sensors.
The end effector largely determines what task a robot can perform; it is often attached as an interchangeable module so that the same robot arm can be reconfigured for different jobs. The position and orientation of the end effector (its "pose") is the central control variable in motion planning.