This is the latest Arduino the UNO Version 'R3'
Plenty of inputs and outputs to connect the Arduino to the outside world!
The USB connection is used to upload 'Sketches' using the Arduino IDE software you can make the Arduino do cool stuff in a matter of minutes!
The possibilities are endless as Arduino is an open source project.
My longest running project is using an Arduino UNO with an Ethernet Shield connected to my Current Cost meter to upload my houshold electricity usage to COSM. You can see the feed here
UNO R3 Specifications:
Operating Voltage 5V
Input Voltage (recommended) 7-12V
Input Voltage (limits) 6-20V
Digital I/O Pins 14 (of which 6 provide PWM output)
Analog Input Pins 6
DC Current per I/O Pin 40 mA
DC Current for 3.3V Pin 50 mA
Flash Memory 32 KB (ATmega328) of which 0.5 KB used by bootloader
SRAM 2 KB (ATmega328)
EEPROM 1 KB (ATmega328)
Clock Speed 16 MHz
Product Code: A000066