The UNO WiFi board is the Arduino UNO with integrated WiFi. The Arduino Uno Wi-Fi is the same as a Arduino Uno Rev3 but with an integrated Wi-Fi module! The board is based on the ATmega328P with an ESP8266 Wi-Fi Module integrated (datasheet). It has 14 digital input/output pins (of which 6 can be used as PWM outputs), 6 analog inputs, a 16 MHz ceramic resonator, a USB connection, a power jack, an ICSP header, and a reset button. It contains everything needed to support the microcontroller; simply connect it to a computer with a USB cable or power it with an AC-to-DC adapter or battery to get started.
The ESP8266 Wi-Fi Module is a self contained SoC with integrated TCP/IP protocol stack that can give access to your Wi-Fi network. (Or the device can act as an access point.) One useful feature of Uno Wi-Fi is support for OTA (over-the-air) programming, either for transfer of Arduino sketches or Wi-Fi firmware.
*Product image shown may be different from actual product sold. However, specifications are correct.
Connectivity – 802.11 b/g/n WiFi @ 2.4 GHz, wake up time < 2 ms; Antenna: PCB and IPX
Misc – Bootloader button, WiFi LED
Operating Voltage – 3.3 V
USB – 1x USB device port
Input Voltage – 5-12 V via DC jack, Vin or USB port (5V only)
Power Consumption – 130 mA (sleepmode 80 mA)
Dimensions – 68.5 x 53 mm
Weight – 28 grams
More info & typical usage
Arduino Uno Wi-Fi board will come pre-uploaded with the RestServer sketch that allows you to control the board via your web browser using the URL: http://192.168.240.1/arduino/<digital|analog>/<GPIO>/<ON_OFF|<INPUT_MODE>, where digital or analog let you select the IO type, GPIO the pin number, ON_OFF is either 1 or 0 for on or off, and INPUT_MODE is either input or output. Some examples: