FreeBSD is a unixoid operating system that is based on the Berkeley Software Distribution (BSD) developed at the University of California in Berkeley. FreeBSD is a stable and reliable system, and runs on numerous processor platforms. Development is focused on optimal performance as well as network and storage functionalities. FreeBSD can be used in servers as well as in desktops and embedded systems. Network services operate reliably under FreeBSD, even under high loads. This is ultimately also the reason why FreeBSD can now be found in various areas of the internet, such as routers, name servers, or web servers.
You can find more information on the project page.