The April board is a break-out for the Imp Developer module. The April module provides the ability to power the Imp module using a standard USB-Mini cable, an optional battery connector, or through a standard .100 header. The April board also has an on-board 3.3V regulator that can with stand an input up to 17 volts and provide 3.3V output of up to 100 mA.
The April board breaks out the 6 pins available on the Imp module. Each of these pins can be configured as digital input / output, PWM and ADC. In addition to these features, each pin can be configured as part of a communication protocol including UART, I2C and SPI.
The April board and the Electric Imp platform are tools that can decrease development costs and improve system security when developing devices for the IoT. The board is also fun for rapid prototyping and experimentation.
The April board costs $10 from Digikey at http://www.digikey.com/product-search/en?keywords=april%20board
The Electric Imp module can be purchased for $25 from Digikey at http://www.digikey.com/product-detail/en/IMP001-US-B/1413-1002-ND/3979639