Barebone laptops?

I'm looking into buying a laptop, and i am very computer savvy. i assamble computers and i use to work for a computer store. But i don't understand what are these BareBone systems?
for example, the MSI S270, is a barebone system, but what does that mean? what do i have to add? and how do i know what are the right parts? and where do i buy them?

thanks for the info.