Facebook uses a lot of servers. A way lot of servers.
Frank Frankovsky thought there were inefficiencies in the design, manufacture and disposal footprint of the commercial servers he was buying, so Facebook started building their own.
What they learned from this endeavor has been embedded in what they're calling the Open Compute Project. The folks over at Business Insider have done a great job describing the project, so if you're interested, head over there for more.
Here's my take.
I really love the idea of Linux - a lot of great stuff is built on it, it's fun and there are a lot of really talented geeks doing amazing things with it (Android is based on it.) It's "open." That means lots of people can contribute, to add their expertise and ideas to improve it.
That also means a lot of great free software: LibreOffice (a very functional replacement for Microsoft Office), Gimp (an alternative to Adobe drawing software), Apache (a popular web server), MySql (the most popular open database server), Asterisk/FreePBX (a PBX for homes and small businesses) - the list goes on and on. The Ubuntu desktop that I'm using on a couple of computers at home is another example - great desktop software that performs well on even old, underpowered computers.
Recently there has been some movement in open hardware that promises some of the same benefits - inexpensive devices supported by communities of interested users and talented geeks. Many 3D printer tools that are appearing on the market are open hardware. The Raspberry Pi, while not technically "open", is moving in that direction. HPSDR (a bleeding-edge "Software Defined Radio") has open hardware. The whole "maker movement" seems to be headed in that direction.
With the backing of Facebook, the Open Compute Project could give this open hardware movement a big boost.
Check it out.