What is the use of the shift operator <<?

Dear All,

I am writing the code for RGB to gray level conversion.
The NTSC standard for luminance:

I = 0.299r + 0.587g + 0.114b

While searching the web, i came across the code that does the task:

#define RGB_SCALE 14
#define cR (int)(0.299*(1 << RGB_SCALE) + 0.5)
#define cG (int)(0.587*(1 << RGB_SCALE) + 0.5)
#define cB ((1 << RGB_SCALE) - cR - cG)

//I is greyLevel output
//r is red value
//g is green value
//b is blue value

I = cR*r+cG*g+cB*b;
I = (((I) + (1 << ((RGB_SCALE)-1))) >> (RGB_SCALE));

What is the purpose of the bitwise operations involving RGB_SCALE, especially for the last line of code?

Thank you.

With Best Regards
HCK