[jdabney]

A system on a chip is a single chip that integrates all or almost all other chips on a motherboard into one chip. So this chip will have a cpu, graphics, memory controller, network controller, io such as usb. That way you can have basically one chip that is all or most of the computer. Sometime RAM and normally storage is separate chips but you basically end up with just a few chips on a very small, normally low power motherboard. It is great for system integrators as they don't need to spend as much development time to build new machines.

[jmtulloss]

It's also great for power and size constraints.