To add to what cperciva said, there's also the difference between the base system (/bin and /usr) and the ports subsystem (/usr/local). Most user space software

To add to what cperciva said, there's also the difference between the base system (/bin and /usr) and the ports subsystem (/usr/local). Most user space software is in /usr/local, which makes is convenient in that you could always solve nasty library/installation problems by removing /usr/local and starting from scratch. The whole of userland and the kernel can also be built with a single command ("make world"). The code is often beautiful and easy to read (my alma mater taught a graduate OS Case Study class where the textbook was "Design and Implementation of FreeBSD" and assignments involved fixing bugs in the FreeBSD kernel) and you get a chance to play with some interesting things (DTrace and ZFS). It really depends on what you're looking for. If you're going to deploy a production web app it may or may not be the best choice (I honestly don't see a big advantage). FreeBSD once used to be lauded for network performance and while it's still excellent, Linux has caught up. Depending on what you're doing e.g., a distributed storage or processing cluster, it may well be worse than Linux (but again, benchmark and stability test it yourself before taking my word for it). If you're curious about operating systems (or are interesting in building your own custom OS without licensing issues e.g., what Juniper did with JunOS), it's perfect.