Corebook p. 236
Humanity does not represent how moral your character is; rather, it is how far removed from the animalistic instincts of the Beast they are. It is essentially a scale between Human and Beast. A high Humanity character may still act callously without incurring Stains if their Convictions and the Chronicle Tenets allow it.
The lower a vampire’s Humanity is, the closer they are to their Beast, and this shows in their appearance. Low Humanity characters don’t move and fidget like living (or high humanity vampires) do, but instead they are unnervingly still unless they consciously make an effort to seem living. Even with Blush of Life, they look more and more corpse-like and their mere presence is unnerving. High Humanity characters, on the other hand, appear more lively and less like corpses, even without Blush of Life.