Raspberry Pi Model A+ is a credit card sized mini-computer board on which you can connect a keyboard or a screen. It is an ARM based mini-computer that lets you run office applications or games. Raspberry Pi Model A+ is also able to play play Hd videos. You can install Linux OS on the SD card on the board.
Raspberry Pi Model A+ is the perfect board for the minimalist Pi fan. This low-cost Pi uses the same processor as the model B+, but does not have an Ethernet jack and three of the USB Ports. This makes it lower power, less expensive and much lighter & smaller. It is still compatible with all Pi operating systems and software, and has the exact same 40 pin GPIO connector and camera/display sockets, so any HATs or Pi Plates or other things that plug into the model B+ will work just the same. It also has the same HDMI, sound/composite connector and microUSB connector for power
Unlike the Raspberry Model B+, there's only one USB port and no Ethernet jack but Raspberry Pi Model A+ is also significantly smaller at 65mm x 56mm if you don't include overhang from the connectors. Also, there is only 256 MB of RAM.
Raspberry PI Models and Revisions:
http://www.raspberrypi.org/documentation/hardware/raspberrypi/models/README.md
Schematics for the Raspberry Pi Model A, B and B+:
http://www.raspberrypi.org/documentation/hardware/raspberrypi/schematics/README.md
BCM2835-The Broadcom processor used in Raspberry Pi Model A, B and B+:
http://www.raspberrypi.org/documentation/hardware/raspberrypi/bcm2835/README.md
Powering the Raspberry Pi:
http://www.raspberrypi.org/documentation/hardware/raspberrypi/power/README.md
USB on the Raspberry Pi:
http://www.raspberrypi.org/documentation/hardware/raspberrypi/usb/README.md
General Purpose Input/Output pins on the Raspberry Pi:
http://www.raspberrypi.org/documentation/hardware/raspberrypi/gpio/README.md
SPI on the Raspberry Pi:
http://www.raspberrypi.org/documentation/hardware/raspberrypi/spi/README.md
Raspberry Pi Web Site: http://www.raspberrypi.org/products/model-a-plus/