Raspberry Pi Zero's UART port

Typically, UART ports consist of a receiver (Rx) and a transmitter (Tx) pin that receive and transmit data. The Raspberry Pi's GPIO header comes with an UART port. The GPIO pins 14 (the Tx pin) and 15 (is the Rx pin) serve as the UART port for the Raspberry Pi:

GPIO pins 14 and 15 are the UART pins (image source: https://www.rs-online.com/designspark/introducing-the-raspberry-pi-b-plus)