This is a cupboard spider (Steatoda grossa), one of the false widow species.
They largely stay hidden, preferring quieter, darker places. I mostly see wandering males, on the hunt for a mate.
Their behaviour (shy, docile) means that we are unlikely to clash, but they have been implicated in bites. It is not dangerous, but I wouldn't want to put a bite to the test. I just remove any from the bedroom/bathroom, I let them be elsewhere. If you're worried about potential bites, put it outside.