Arduino Uno WiFi Developer Edition is a retired 'Made in Italy' board developed and produced by arduino.org
Arduino UNO WiFi Developer Edition is an Arduino UNO R3 with ESP8266 integrated on the board. It was developed and manufactured by Arduino.org.
UNO WiFi Developer Edition connects ATmega328 to ESP8266 using additional on board UART chip SC16IS750. This additional UART is connected to ATmega as I2C device.
The Arduino.org team did use a JeeLabs ESP-link with minor changes for the firmware of the UNO WiFi Developer Edition.
With IDE 1.8.x the library for the Atmega side of this firmware is “Arduino UNO WiFi Dev Ed Library”. The network communication possibilities are limited to port 80 and MQTT. The library can be installed with Library Manager in IDE.