What do these pins mean? Where should I plug them in?
This is called the SPI interface (See Serial Peripheral Interface, Wikipedia. The pin names typically used for SPI are:


GND : Power Ground
VCC : Power input
CS : Chipselect
SCK/SCLK (SD-Clock): SPI Clock
MOSI (SD-DI, DI) : SPI Master out Slave in
MISO (SD-DO, DO) : SPI Master in Slave out
CD: Card Detect (see comment of rollinger below (thanks).


On an Arduino Uno the SPI pins are:


CS – digital 10; this can be in principle any pin
SCK – digital 13
MOSI – digital 11
MISO – digital 12