Uprated Headlight Wiring Loom

Hi,

I have a 1990 1.6 diesel caddy and am considering fitting a plug and play uprated wiring loom for the headlamps.  I have previewed the fitting instructions and see that they tell me to unplug and remove the ballast resistor.  Can anyone tell me what the ballast resistor does, where I can find it, and if disconnecting it will have any consequences?

Thanks