Why does NASA say that astronauts are in “zero g”?

As you’ve learned, there is gravity everywhere in space, so what exactly does it mean when you hear NASA talk about “zero g” conditions in space? The “g” actually refers to the effects that you feel from acceleration, in the same way that you may have heard pilots sometimes describe the forces they feel in “gees.” For example, during a rapid acceleration, a pilot might experience a force of “3 gees.” The “gee” is just the pronunciation of the small letter g, which stands for the acceleration of gravity on Earth, which determines your normal weight. Therefore, saying that a pilot is experiencing a force of “3 gees” means the pilot is feeling 3 times as much force as they normally would feel from gravity on Earth. In essence, the pilot would feel like she has 3 times her normal weight pressing down on her due to the rapid acceleration of her jet.
This type of terminology is used quite often. For example, we sometimes refer to the force we feel due to gravity on the surface of Earth as “one g.” And because the acceleration of gravity on the Moon is about 1/6 that on Earth, we would feel a force of “1/6 g” on the Moon.
So what does “zero g” mean? It means conditions in which you don’t feel the effects of the gravity, because you are in freefall or in space and hence are weightless. In other words, “zero g” means “zero force that you feel.” Note that it does NOT mean “zero gravity,” since there is gravity everywhere, even though it is sometimes misinterpreted in that way.