weightlessness
Weightlessness is that floating feeling astronauts have, drifting freely inside their spacecraft with nothing pressing on them. You can taste a hint of it yourself: the brief lightness in your stomach when a lift starts dropping, or at the top of a roller-coaster hill. It is the sensation of having no support beneath you.
Here is the key idea, and it surprises almost everyone: weightlessness is not the absence of gravity, it is free fall. When you and everything around you accelerate downward together at the same rate g, nothing has to push up on you to hold you in place. The floor is falling away just as fast as you are, so it presses on you with zero force. Since the support force is what your body registers as weight, that force being zero is what makes you feel weightless. Your true weight, the gravitational pull m g, is still fully present.
This is why astronauts float even though, at the space station's altitude, gravity is still about 90 percent as strong as on the ground. They are not beyond gravity; they and their station are simply falling around the Earth together, endlessly. The condition is often called zero-g or microgravity, though calling it zero-gravity is a bit misleading, since gravity is exactly what keeps them in orbit.
In a lift whose cable is cut, a bathroom scale under your feet would read zero: you and the scale fall together at g, so neither pushes on the other. That is exactly the astronaut's situation, prolonged forever by orbiting instead of hitting the ground.
Free fall makes the support force vanish; the scale reads zero even though gravity is fully at work.
Weightlessness is free fall, not zero gravity; at orbital heights gravity is still nearly as strong as on the ground, and true weight m g never disappears.