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

What is  ∀v_n(φ)? I forgot what ∀ means and how a variable v_n can be a function.

What is ∃v_n(φ)? I forgot what ∃ means and how a variable v_n can be a function.

"If v_n is a "free variable" in φ, then "∀v_n(φ)" is a valid formula and v_n is NOT a free variable in φ (for every 'vn'...)"

If v_n is a free variable, then it's not a free variable? I don't get it