Weightlessness is a condition experienced when an object is in free fall, meaning it is falling under the influence of gravity without any other forces acting on it. This sensation occurs in space, such as aboard the International Space Station, where astronauts and objects float because they are all falling towards Earth at the same rate. In this state, the effects of gravity are still present, but they are not felt as weight. This is why astronauts can move freely and perform tasks without the burden of their own weight, creating a unique environment for scientific experiments and daily activities in space.