Adafruit Product Code: 2231
The Raspberry Pi Compute Module is Raspberry Pi's new product 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.