What is gravity?

You ask: What gravity?

Caveman drop rock. Rock fall. Why? All big heavy things bend space around them, like fat mammoth sleep on stretched hide — hide sag, berries roll toward mammoth. Earth very heavy, so space sag around Earth. Caveman, rock, river — all slide down sag toward Earth middle. More heavy thing, more sag, more pull. Moon not fall on head because moon move sideways fast — moon fall toward Earth forever but keep missing. That called orbit. Even Caveman have tiny pull, but Caveman too small — sag too little to feel. Sun sag biggest of all — sun heavy as three hundred thousand Earths — so Earth slide around sun. Cave wisdom: gravity not sky-hand grab thing down. Gravity is heavy things making dents in space, and all things roll toward dent.