FUNDAMENTALS OF COMPUTER

Detailed explanation-1: -Raspberry Pi can communicate serial data with other devices using some of the common serial communication protocols, such as UART, I2C, SPI, and USB. There are two UART ports/interfaces, two I2C ports (one for HATS and other for external devices), two SPI ports, and four USB ports on RPi 3B/4B.

Detailed explanation-2: -Technically, the Raspberry Pi has two UARTs: PL011 UART and mini UART. However, you only have one pair of TXD and RXD pins to work with. The PL011 UART is the main UART for models without Bluetooth feature and is tied directly to the Linux console output.

Detailed explanation-3: -UART-Universal Asynchronous Receiver/Transmitter UART is commonly used on the Pi as a convenient way to control it over the GPIO, or access the kernel boot messages from the serial console (enabled by default). It can also be used as a way to interface an Arduino, bootloaded ATmega, ESP8266, etc with your Pi.

Detailed explanation-4: -Raspberry Pi uses UART (Universal Asynchronous Receiver/Transmitter) is a serial communication protocol in which data is transferred serially i.e. bit by bit. Asynchronous serial communication is widely used for byte oriented transmission.