Is Chip fan/fan 3 really necessary?

When I boot my computer, the case fan and the CPU fan spin correctly, but I sometimes get a warning saying that the chip fan is not running. When I view hardware status in the bios I see that indeed the chip fan is not running, and generally if I wait 3-5 mins in that bios screen the chip fan automatically starts to run.

Once, I ignored the warning, loaded windows, and with Speedfan I can see that the chip fan is fan3 and it wasn't running. The CPU temp is at 30-35 degrees (not big programs running) Celsius so its not a big deal.

What is this chip fan/fan 3 exactly? Is it the small thing that looks like a fan but has a metal cover with the asus label on it? It is located directly southeast of the video card? If such is the case, is such a small fan really necessary to the cooling process?

My room temperature is generally 16-18 degrees Celsius and I leave my case open when my pc is running, dust my desk every few days and put the case lid back on at night.

Or perhaps chip fan/fan3 is the GPU fan?

Thanks for any info.