This is a BRAND NEW OEM York/Luxaire/Coleman Gas Furnace HSI Kit (Hot Surface Ignitor Kit). The York/Coleman/Luxaire Part # is 473-20937-001 which replaces all the old part #s listed below. Several older less reliable ignitor designs have been superceeded into this one. If you need to make the change the kit includes the necessary hardware.
The purpose of an ignitor is to ignite the gas after the gas valve opens up. It most cases, the ignitor turns off after ignition has occurred.