You can read about it on the FreeBSD website — https://freebsdfoundation.org/freebsd-project/what-is-freebsd/
Over Linux I assume? It has some unique stuff, like ZFC completely integrated. There's monolithic approach, Linux is just a kernel with a lot of distros, while with bsd kernel, userland and utilities are developed together. Some people say that is also more simple and logical than Linux. In my opinion both are good, it just depends on your use case.
Also most of ppl who use BSD use Linux too from my experience.