What is the Wire.h library? What does it do? Why it is in the Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET); What is the OLED_RESET?

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What is display.begin(SSD1306_SWITCHCAPVCC, 0x3C); ?

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 byte qrcodeBytes[qrcode_getBufferSize(qrVersion)];        //??????????
qrcode_initText(&qrcode, qrcodeBytes, qrVersion