Why?

I like forking and for some reason I always find myself pleased when I fork an opponent.

Hey kids, isn't chess fun?!  Today we learn about how bishops can fork too!

Also it could take the knight on c6, put the king in check, and take the rook.

I always have called those a split attack.  To me, a knight fork is just a little different, because, or the most part, when a knight forks none of the chessmen being attacked can counter attack.  Of course, in the position you gave, neither of the knights can counter attack, but that is usually not the case. At least not in my games it hasn't been. 

There is no difference in central control and no difference in b and g pawn protection when you change the move order from 3.Nf3 4.Bb4 to 3. Bb4 4.Nf3 -- central control and knight pawn protection have nothing to do with this tip on move order for beginners.

Oh, yes!  And even more so when my opponent didn't see it coming.  Like when you hear, "Woo, I didn't see that!!"

Heh yeah, it could be two forks in a row, good point.

So something like this could happen too, the common idea of the rook and king fork.

All right, all right, no need to be sarcastic.

Yes, and isn't it sweet?  It's like catching a two bank robber and you are armed with a magnum 44 and they aren't armed at all.  

 In that case, the knight could move e6, and protect the bishop.

 Shouldn't the bishop be in d7?

If you mean in the final position, then bishop takes rook wins material.

But in the diagram I did make it with white missing his queen's knight for some reason (?) I'll fix that.

I was just meaning that black's bishop couldn't take the knight without starting out in d7.

Oh yeah -- this is just a position I made for the purpose of a bishop fork.  I made black waste time with a move like g6 and gave white a4 to protect his bishop (so that after Nxc6 Qd7 doesn't work anymore).

A lot of times you see beginners push a6 in a position like this though.  My advice is either play a6 immediately (like a ruy lopez) or don't play until you've castled.  Nearly every position I've run into with a late a6 (and before castling) loses a pawn for black.

 Okay.

Opps! I meant to say, Bishops move faster than knights. That is the main reason behind moving Knights first. In the development stage, speed is critical.

You can control more space faster by moving knights first, since they can control four attacking squares and four defensive squares placed on the c3 and f3 squares, for a total of eight squares.

Withholding the bishops, in general, affords the player more flexibility in the opening phase. Bishops have the potential to control more squares when placed on long, open diagonals, and like knights, control the greatest number of squares when placed in one of the four key squares. 

Bishops can control squares from a distance, whereas, knights must relocate to control another set of four attacking squares.

Maybe I should give the Ruy Lopez a spin and bring out my bishop on move three and castle on move four. At least I won't get checkmated in ten moves or less with a safe king.

The rationale for knights before bishops that I was taught back in the day was that knights are more powerful early in game, when positions are more closed, and bishops gain power as the board becomes more open towards the endgame.