expletive it / anticipatory it

Expletive it is a dummy subject. It fills the subject slot and does not point back to a noun: It is raining. It is a long way. It is too late. Expletive here means a filler word, not a swear word. Anticipatory it is that same dummy it when the real content comes later: It is clear that the pump failed. The it holds the place of the clause that follows. Both are standard.