Learn Spanish (Latin America): El baño está abajo.

Debajo de means "under" or "underneath" something specific, like debajo de la cama (under the bed). When you just want to say "downstairs," "down," or "below" as a general location without pointing out exactly what it is under, you just use abajo.

Does abajo always translate to "downstairs"?

Not always! It generally means "down," "below," or "at the bottom." However, when you are talking about the layout of a house or building, abajo is the standard and most natural way to say "downstairs." Its opposite, "upstairs," is arriba.

Why do we use está instead of es here?

We use está (from the verb estar) because we are talking about physical location. A common trap for learners is thinking that because a bathroom is permanently built into a house, it should use ser. But in Spanish, you must always use estar to say where someone or something is located, no matter how permanent it is!