This integrated board is perfect for wireless applications and is the same size as the original UNO. It is based on the ATmega328 MCU together with the ESP8266 WiFi module. The WiFi element is a self-contained SoC with integrated TCP/IP protocol stack giving you access to a WiFi network. One of the main advantages of this is its support of OTA (Over-the-air) programming.
The Uno is a microcontroller board based on the ATmega328P. It has 14 digital input/output pins (of which 6 can be used as PWM outputs), 6 analog inputs, a 16 MHz quartz crystal, 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 a AC-to-DC adapter or battery to get started. You can tinker with your UNO without worrying too much about doing something wrong, worst case scenario you can replace the chip for a few dollars and start over again.

Power

The Uno board can be powered via the USB connection or with an external power supply. The power source is selected automatically. External (non-USB) power can come either from an AC-to-DC adapter (wall-wart) or battery. The adapter can be connected by plugging a 2.1mm center-positive plug into the board's power jack. Leads from a battery can be inserted in the GND and Vin pin headers of the POWER connector. The board can operate on an external supply from 6 to 20 volts. If supplied with less than 7V, however, the 5V pin may supply less than five volts and the board may become unstable. If using more than 12V, the voltage regulator may overheat and damage the board. The recommended range is 7 to 12 volts.

Memory

The ATmega328 has 32 KB (with 0.5 KB occupied by the bootloader). It also has 2 KB of SRAM and 1 KB of EEPROM (which can be read and written with the EEPROM library).

Communication

The Uno has a number of facilities for communicating with a computer, another Uno board, or other microcontrollers. The ATmega328 provides UART TTL (5V) serial communication, which is available on digital pins 0 (RX) and 1 (TX). An ATmega16U2 on the board channels this serial communication over USB and appears as a virtual com port to software on the computer. The 16U2 firmware uses the standard USB COM drivers, and no external driver is needed. However, on Windows, a .inf file is required. The Arduino Software (IDE) includes a serial monitor which allows simple textual data to be sent to and from the board. The RX and TX LEDs on the board will flash when data is being transmitted via the USB-to-serial chip and USB connection to the computer (but not for serial communication on pins 0 and 1).

Datasheet
Arduino Uno WiFi Development Board Datasheet

Processor
Clock Speed	Uno (16MHz), WiFi (80MHz)
Microcontroller	Uno (ATmega328P), WiFi (ESP8266 - Architecture Tensilica Xtensa LX106)
Power
Input Voltage (Limit)	6-20V
Input Voltage (Recommended)	7-12V
Operating Voltage	Uno (5V), WiFi (3.3V)
Memory
EEPROM	1KB
Flash Memory	Uno (32KB), WiFi (4MB)
SRAM	2KB
Technical
Analog Input Pins	6
Communication	I2C, SPI, UART (TTL)
DC Current for 3.3V Pin	50 mA
DC Current per I/O Pin	20 mA
Frequency	2.4GHz WiFi, 802.11 b/g/n
Input/Output	14 (of which 6 provide PWM output)
PWM Digital I/O Pins	6
Physical
Dimension	68.6 mm (L) x 53.4 mm (W)
Weight	25 g