Arduino Uno is a microcontroller board based on the ATmega328P (datasheet). 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. 

Features:

• Microcontroller: ATmega328P
• Operating Voltage: 3.3/5V
• Input Voltage: 1.8-5V
• DIO Pins: 14 (of which 6 provide 'PWM' output)
• AIO Pins: 6
• DC Current per I/O Pin: 20 mA (40mA peak)
• DC Current for 3.3V Pin: 50 mA
• Maximum Board Load Current: 200mA
• Flash Memory: 32KB (ATMega328P) of which 0.5 KB used by bootloader
• SRAM: 2KB (ATMega328P)
• EEPROM: 1KB (ATMega328P)
• Clock Speed: 16MHz
• System Bus: 8-bit
• USART: 1
• Serial TTL, SPI, I2C support
• Timers - 3
• External Interrupts, Supply & Clock support