FreeBSD UNIX system can be updated in many ways. You can use freebsd-update(8) command to fetch and install the official binary patches. You can download the FreeBSD sources and compile your new version. You can download and install base.txz and kernel.txz sets in a new ZFS Boot Environment along with copying over your config files there – Other FreeBSD Version in ZFS Boot Environment – as documented here.
While for most users these three options will be more then enough – there is a small group or people that need something else. Companies. People that like to use custom FreeBSD version or enterprise corporate world that needs to fulfill many compliance regulations. For their multiple reasons – including but not limited to – security – they want to have their own trusted FreeBSD update infra under their control.↫ vermaden
It’s from vermaden, so if you’re a FreeBSD user, you know you’re getting good information. Their website is a treasure trove of incredibly detailed information about pretty much everything related to installing, running, and living with FreeBSD.