In Star Trek: The Original Series, a tricorder allows a crew member to scan a planet's atmosphere, terrain, and life signs.
The tricorder is a portable multi-purpose sensor and data-processing device carried by Starfleet personnel. Science and medical variants can collect different kinds of information, while the standard model supports environmental readings, recording, and analysis.
Away teams use tricorders before and during planetary exploration. The device can detect unusual radiation, identify life forms, measure atmospheric conditions, and store readings for later study. Its folding design and handheld display became one of the most recognizable pieces of Star Trek technology.
A tricorder is sometimes confused with a communicator, but the two devices serve different purposes. A communicator handles voice communication and location signaling; a tricorder is primarily a portable scanning and analysis instrument.