To experience gravity you have to be close to something with mass. In space it’s mostly vacuum so there’s more gravity when you’re near planets, stars etc and less when you’re further away. For astronauts on the International Space Station, it’s more like microgravity / free falling. They have a tiny bit of gravity but barely any because they orbit around the Earth at a high enough velocity (28,000km/hour) that they go forward fast enough to escape this pull of gravity down and end up moving around and around and around the Earth. So astronauts and the ISS are always freefalling and the Earth curves beneath them so they never get any closer and they are ‘weightless’!