System on a chip (SOC) vs CPU...
ARM, Nvidia Tegra, Apple A4 vs Intel Atom

Apple A4 SOC unveiled - It's an ARM CPU and the GPU! - Bright Side Of News*

Apple's A4 Chipset Packs ARM CPU and Graphics

Nvidia Unveils Tegra: A Computer On A Chip

ARM based CPU is used in most SmartPhones
and Intel Atom in most of Netbooks...