What was the term 'terminal' that often appeared in interstellar novels?

The term " terminal " often appeared in interstellar novels. It usually referred to an existence similar to the end of the universe. It was the final destination of interstellar travel and the place where various civilizations met. In the novel, this terminal could be a mysterious planet, an unknown black hole, an unknown spatial rift, and so on. In interstellar travel, different civilizations might use different technologies to explore and conquer the terminal. Some civilizations may use powerful weapons and technology to attack the terminal, while others may use mysterious energy to approach the terminal. The terminal itself may have different characteristics and powers. Some of the terminal may be safe, while others may hide dangerous and unknown powers. The Terminal was a very important character in interstellar novels. It was a symbol of unknown territory, unknown power, and unknown civilization in interstellar travel.