Zero gravity, or zero-g, is one of those terms that was used in sci-fi before it was needed in reality.
Arthur C. Clarke
wrote about zero “g” in Islands in the Sky
in 1952, making it the first time the idea was shortened this way. Many, many authors since have written about the apparent absence of gravity in space, and about people adapting to lower gravity environments like the Moon.
In the real world, the term microgravity is preferred to zero-g because gravity is never really gone. Even if your spaceship is way out beyond the Earth and Moon, there is some small yet measurable force of gravity acting upon you. Astronauts working in orbit around earth experience weightlessness because they are in freefall – they are indeed still affected by Earth’s gravity, but they are also in a vessel that is moving forward. Effectively, they are “falling around” the Earth – the forward motion cancels out the downward motion, and everything inside the ship floats.
Would you like to experience zero-g?