Question about this method.

[gjon]

Here's a simple example:

class Bird {  
    int xPos, yPos;  
  
    double fly ( int x, int y ) {  
        double distance = Math.sqrt( x*x + y*y );  
        flap( distance );  
        xPos = x;  
        yPos = y;  
        return distance;  
    }  
    ...  
}

Can someone explain what this part:
flap( distance );
does, or what is happening with it? How is it being used? Is it a method inside the fly method?

Also:

class Bird {  
    int xPos, yPos;  
    int xNest, yNest;  
    ...  
    double flyToNest( ) {  
        int xPos = xNest;  
        int yPos = yNest:  
        return ( fly( xPos, yPos ) );  
    }  
    ...  
}

How is the return statement working here?
return ( fly( xPos, yPos ) );
I know these are examples, but they are confusing me as it seems they are leaving things out. Whats being left out?
Thanks in advance for clearing it up.