The Raspberry Pi 3 is here to provide you with the same Pi as before but now with double the ram and a much faster processor. The biggest change that has been enacted with the Raspberry Pi 3 is an upgrade to a next generation main processor and improved connectivity with Bluetooth Low Energy and BCM43143 WiFi on board. The Raspberry Pi 3 has improved power management, with an upgraded switched power source up to 2.5 Amps, to support more powerful external USB devices. The Raspberry Pi 3's four built-in USB ports provide enough connectivity for a mouse, keyboard, or anything else that you feel the RPi needs, but if you want to add even more you can still use a USB hub. Powering the Raspberry Pi 3 is easy, just plug any USB power supply into the micro-USB port. There's no power button so the Pi will begin to boot as soon as power is applied, to turn it off, simply shut down the Pi 3, then remove power. The four built-in USB ports can even output up to 1.2A enabling you to connect more power hungry USB devices.
Dimensions: 85mm x 56mm x 17mm
Look here to see our Raspberry Pi tutorial