How does pure ammonia and household ammonia differ?

Ammonia in its pure state is a single molecule (NH3) which, depending on pressure, can be either a liquid or a gas.

Household ammonia (aqua ammonia) is a solution of ammonia in water which is usually described as NH4OH or as its componest ions NH4+ and OH-

If you had pure ammonia in a container (as a liquid) it would rapidly change to ammonia gas. An ammonia solution (household ammonia) is much more stable.