The Raspberry Pi Compute Module is Raspberry Pi's specifically designed for makers who want to develop and build their own PCBs.  It has most of the power of a Raspberry Pi B+ without some of the bells and whistles.  This gives it a much smaller footprint (68mm x 30mm), allowing you to build off of your Pi without having to carry around your credit card sized computer.

The compute module has a BCM2835 chip with 512MB RAM and 4GB eMMC flash memory - which is the equivalent of a SD card in your Raspberry Pi.  The board fits into a DDR2 SODIMM connect - which is used for your laptop's memory.  This doesn't mean you can stick the compute module into your laptop but it does mean setting up the compute within a custom system should be relatively easy.

there are some items needed to start with RPi you can click on the name of the item to go to buying page:

HDMI Cable

an SDcard 

a USB Mouse & Keyboard 

monitor if you don't have (any HDMI one works)

Power source