Good FreeBSD question — answering as the UphillTech team:
If you want to know what's different so you can use the system more efficiently, here is a commonly referenced introduction to BSD to people coming from a Linux background . If you want more of the historical context for this decision, I'll just take a guess as to why they chose FreeBSD. Around the time of the first dot-com bubble, FreeBSD 4 was extremely popular with ISPs. This may or may not have been related to the addition of kqueue . The Wikipedia page describes the feelings for FreeBSD 4 thusly: "…widely regarded as one of the most stable and high performance operating systems of the...
Full answer by Hank Gay: https://unix.stackexchange.com/a/14491 (CC BY-SA 4.0).
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