Don't get it confused with a WiFi dongle! The Digispark is a full-blown development board the size of a coin. It is based on an ATtiny85 microcontroller, which comes from the ATtiny line of MCUs, also known as TinyAVR. It is a cheaper and smaller alternative to the Arduino UNO's ATMega328P. The best thing about the Digispark is its plug and play. No need to have a USB connector as the board itself is a USB type-A male plug.

Specifications:

• Support for the Arduino IDE 1.0+ (OSX/Win/Linux)
  
• Power via USB or External Source - 5v or 7-35v (12v or less recommended, automatic selection)
  
• On-board 500ma 5V Regulator
  
• Built-in USB
  
• 6 I/O Pins (2 are used for USB only if your program actively communicates over USB, otherwise you can use all 6 even if you are programming via USB)
  
• 8k Flash Memory (about 6k after bootloader)
  
• I2C and SPI (vis USI)
  
• PWM on 3 pins (more possible with Software PWM)
  
• ADC on 4 pins
  
• Power LED and Test/Status LED

Inclusions: 1 x Digispark Development Board 

Documents: 

• Schematic
• Eagle File