The relative pronoun was


Referring to a whole phrase

In order to refer to a phrase rather than just a noun the relative pronoun was ‘which’ introduces the relative clause:

Sie arbeitet jetzt nur vormittags, was ich gut finde.
She now works only in the morning which I think is good.
Sie möchten nach Australien fliegen, was sehr teuer ist.
They want to fly to Australia which is very expensive

In connection with alles, etwas, nichts

was is also used when referring to the pronouns alles ‘everything’, etwas ‘something’, nichts ‘nothing’ in the main clause.
Sie konnte sich an nichts erinnern, was vor dem Unfall passiert war.
She couldn’t remember anything that had happened before the accident.
Alles, was sie sagte, machte Sinn.
Everything she said made sense.
Das ist etwas, was ich nicht ausstehen kann.
That is something I cannot stand.