I2C, or Inter-Integrated Circuit, is a synchronous, multi-master, multi-slave, packet-switched, single-ended, serial communication bus widely used for attaching lower-speed peripheral ICs to processors and microcontrollers in short-distance, intra-board communication. It operates using only two bidirectional open-drain lines, SDA for data and SCL for clock, making it efficient for simple communication setups with minimal wiring.