Introduction
CAN is a specification for communication between distributed microcontrollers, especially those embedded in large machines. Data throughput depends on distance and ranges from 125 Kbps (for up to 500 m) to 1 Mbps (for up to 40 m). It is therefore complements the short-range, high-speed communication specifications SPI and I2C.
Please read the Wikipedia entry on CAN for more information.