In The Terminator, the cyborg assassin uses the model designation T-800.
The T-800 is a Cyberdyne Systems Model 101 infiltrator sent from 2029 to 1984. It has a living human-tissue exterior over a metal endoskeleton, allowing it to pass as a person while carrying out its mission.
The film does not usually call the character simply “T-800” in dialogue; “Terminator” is the common name for the role. Arnold Schwarzenegger plays the machine, while Michael Biehn plays Kyle Reese, the soldier sent back to protect Sarah Connor.
The later films introduce other designations, including the liquid-metal T-1000 and the female-shaped T-X. Those are separate Terminator models, not alternate names for the original machine in the 1984 film.