Transform origin is the point around which CSS transforms rotate, scale, or skew. By default, transforms pivot at the element’s center, but changing this origin moves the pivot point so the transformation happens around a different spot. You can set it with values like 25% 75%, left top, or explicit lengths like 10px 20px, and even include a depth value for 3D with a z coordinate (for example, 50% 50% 5px). This is what makes an element rotate around its top-left corner or around any other chosen point instead of its center. Other properties don’t define that pivot. The transform property applies the actual transformation functions; perspective-origin determines where the vanishing point for perspective projection is placed, and transform-style controls whether 3D transforms are preserved for child elements.