Originally Unix was owned by AT&T and BSD was based on the source code from this time. When AT&T spun off Bell Labs it was freed from being required to license Unix for free. In 1984 Bell Labs wanted license feeds for Unix. This did not go over well and open source quickly moved to develop new code to replace the old AT&T code.
Back in 1993 a new CD-ROM was available with FreeBSD. This operating system was 32-bit which was better than anything that DOS or Windows was doing at the time. While FreeBSD was a developers platform, it was clear there was a lot of work to be done. The main advantage was the native 386 code mean no problems with program design or memory management issues. At this time there was still some legal wrangling over Unix and other operating systems. Eventually FreeBSD was updated to a new BSD 4.4 core which eliminated legal problems with a new code base.
FreeBSD over time expanded considerably. Much of what is seen today with Linux actually originally started with FreeBSD a decade earlier. Today FreeBSD and Linux are nominally the same with open source packages widely available for each of them.
Today FreeBSD is widely seen with network attached storage. It’s small enough to run from a USB stick which affords all hard disks as pure data.