WHITE Knight F3 Opening - Huh??

I'm new to seeing this opening (very rare from my experience) and wondering if there is a name for a system based on this move and what might be good responses to it? 

TVM!  

you are facing the Reti opening a hypermodern system aimed at controlling the centre with pieces initially not pawns a revolution in chess thinking at the time now accepted as a solid opening choice for white

taking up the challenge can go a few ways the main seems to be black occupying the central squares with his pawns but that can be difficult to maintain if white wants to contest it

1.Nf3 is far from being the Reti opening yet. It's a transpositional tool that can lead to Reti, English, all kinds of d4-openings and sometimes even the Sicilian.

Interesting, guys.  

I'll have to look more into this.  But it just seems very rare for me to see opponents do this sort of opening.  

Is there any ONE (or two..) moves that BLACK should reply with from the get go to respond to Nf3 by WHITE?  I'm usually literally confused by this and am not sure what to open with after seeing Nf3.  Thanks again! 

Any reasonable move. Mostly black plays 1...d5, 1...c5 and 1...Nf6. Especially the last of these can lead to any closed type opening except for the Dutch.

I wouldn't call it rare, it's probably the most common first move behind 1.e4 and 1.d4.