The Rev C has a blistering 1GHz AM3358 processor and 512MB onboard DDR3 RAM, two 46-pin headers, micro HDMI for audio/video output, USB ports, 10/100 Ethernet and other I/O features. The Rev C is an ultra-powered embedded computer that can fit in a mint tin.
This model includes 4GB of eMMC built-in storage instead of the Rev B's 2GB. With the doubled storage and faster eMMC, the developers were able to make the Rev C's most significant change: shipping the BeagleBone Black with Debian Linux pre-loaded on the board's flash instead of Angstrom Linux. Debian Linux is a more user-friendly operating system than Angstrom and the switch to Debian is partly the result of consumer demand (especially from Adafruit users, thanks!)
Of course the BeagleBone Black Rev C is an open board so if you want to load it back up with Angstrom or other Linux-based distributions like Ubuntu or Android, you can.
The rev C comes with a mini-B cable for powering it up ASAP. No microSD card is included as the BBB has onboard flash storage - and no SD card loading is required to get started