User blog comment:DontDrinkH20/H-Boogol-Boogol Bit by bit: PART 1: Model Theory 101/@comment-31966679-20180901210309/@comment-36540075-20180901225056

That's the typo PiBot was talking about! Oops, couldn't tell what he meant.

∀ means "forall", so for example "∀v_0(v_0 + 1 > 0)" is "for every v_0, v_0 + 1 is bigger than 0". Then ∃ is the "there exists" counterpart.