Please don't post in ALL CAPITALS!

The '2' in "I2C" should really be a superscript, meaning "squared:"
I2C = IIC = Inter-IC - it is a proprietary 2-wire bus standard devloped by Philips for interconnecting Integrated Circuit subsystems within (usually) equipment.
The 2 wires are a clock and a data line.
You can find the details on the Philips site.

"2-Wire" refers to an interface which uses 2 interconnecting wires;
"3-Wire" requires 3 wires;
"4-Wire" requires 4 wires;
... you get the idea!?

There is some ambiguity as to whether the number of wires includes the ground connection or not; eg,
The "2-Wire" reference to I2C requires an extra ground connection, as does the "1-Wire" of the Dallas "1-Wire(TM) bus"

However "3-Wire" - especially in the context of a "3-Wire RS232 Link" - includes the ground: TxD, RxD, GND.

"4-Wire" in the context of telephone circuits usually means a total of 4 wires; 2 for transmit & 2 for receive.

Hope that makes some sort of sense!?