A relative adjective relates the owner to that which is owned, as does the English "whose". It is always next to a noun. The relative adjectives are: cuyo, cuya, cuyos, cuyas. Let's look at some examples of proper use:

Es la mujer cuyo hijo se ha muerto.
It is the woman whose son has died.

El café cuyo origen desconozco, me gusta.
The café, whose origin I don't know, I like.

La casa, cuya puerta está cerrada...
The house, whose door is closed...

¿Eres el hombre cuya empresa necesita publicidad?
You are the man whose company needs advertising.

Son los hombres cuyos hijos trabajan en el banco.
They are the men whose children work in the bank.

Es el pintor cuyas obras fueron expuestas en Madrid.
It is the painter whose works were shown in Madrid.