Hi, I2C is a serial commn. protocol invented and patented by Philips. it uses two lines SCL (Clock) and SDA (Data) to communicate among different devices. More info. on I2c will be available on philips semiconductor's web site.
2 wire, 3 wire etc. commn. simply indicates the number of lines or paths used to exchange information among devices.
Detail explaination of all this is not possible here. better u search the web.
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