Trying to understand how index funds truly work/how the price moves up and down

How does the price move?

If every single person holding shares in $VOO decided to sell would it cause the price to plummet like a normal security would in that scenario?

Or are the price of index funds independent of the current market price, and only mirror the underlying securities?

If I buy 1 share of VOO, am I essentially just giving money to Vanguard who has purchased the underlying securities?