Third Switch from the left

Can somebody help me? I bought a 2000 MG F Steptronic, I'm in Portugal, my English is bad, I still know bad carr, on the switches, the third trailing switch rem a red light that comes on when I turn the key on and off as soon as the motor starts working, today lighted with the car running and abow and also triggered a buzz, the first switch serves to open/close the window from the left, the second does not have any switch, the third is that I'd like to understand what it's for, the fourth is the fog. Waiting for information, jvcp1@sapo.pt

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