Arduino Uno R3 is the clone one of the latest version of Arduino Uno with an on-board CH340 usb - serial converter chip. Even there are some little differences respect to original one, it is almost the same in terms of usage and software. This provides you a cheaper opportunitiy to get started with Arduino boards.
The microcontroller model of this board is the same as the original one (Atmega328). The only difference between microcontrollers is ther package. Original one has a DIP package but the clone one has SMD package microcontroller.
Despite being a clone one, there are a pin group (4x GND, 2x 5 V, 2x 3.3 V, 1x RX/TX, 1x SCL/SDA) near to the crystal oscillator and there are external pin holes allow you to solder male headers on the board too.
Arduino Uno SMD CH340 Driver Features
Operating voltage: 5V
Input voltage (recommended): 7-12V
Input voltage (limit values): 6-20V
Digital I / O Pin 14 (6 of them provide PWM output)
PWM Digital I / O Pinlar: 6
Analog Input Pin: 6
DC current per I / O Pin: 20 mA
3.3V Pin DC current: 50mA
Flash Memory 32 KB (ATmega328P) which is used by the 0.5 KB bootloader