What does the opening chess move Nf3 Nf6 mean?

Answer 1

That is algebraic notation. The N stands for kNight (K is King). The notation tells us that White's Knight moved to F3 and Black's Knight moved to F6. The notation doesn't need to tell us the starting point for the pieces, logically it can only be White's Knight from B1 and Black's from G8, and in general algebraic notation will only mention the start point if there's any ambiguity (ie for two white rooks who can both arrive at an intersection of their paths at F5, you'd have to say which it was)