How to use SPI in Arduino: Communication between two Arduino Boards

A Microcontroller uses many different protocols to communicate with various sensors and peripherals. There are many protocols for wireless and wired communication, and the most commonly used communication technique is Serial Communication. Serial communication is the process of sending data one bit at a time, sequentially, over a communication channel or bus. There are many types of serial communication like UART, CAN, USB, I2C and SPI communication.