The two words get used as if they mean the same thing. They don't — and the difference is why some skin stays dull and tight no matter how much cream you apply.
Hydration is water in the skin. It comes from humectants — ingredients like hyaluronic acid and glycerin that draw water in and bind it where skin needs it.
Moisturization is keeping that water there. It comes from emollients and lipids that soften the surface and reinforce the barrier so water doesn't simply evaporate away.
Dehydrated skin is short on water. Dry skin is short on oil. Most skin, most of the time, needs both — in that order. Balance pairs multi-weight hyaluronic acid to hydrate with barrier-supporting lipids to seal, so the water you put in stays in.