Most call them Jails, but others like to call them containers. But in comparison to Linux containers they are very different. Some would argue what you can do in jails you can do in Linux containers but, that's another discussion.
Each Jail, can have it's own network adapter, allowing yourself to host network applications, firewalls, servers and routers isolated from your main network.
These jails can have firewalls allowing you to test firewall changes without burning down your network. As well as isolated Web Servers, Music Servers, Game Servers taking no further resources other than what you give it.
You can also apply resource limits to jails, and the whole lot too. IOPS, CPU Cycles, Cores, Network, Quota Size.
With this you can then create locked sandbox environments for applications. Firefox/chromium can all run in their own jail ensuring that any virii are isolated from your core system while ensuring they only have 2mbit of network. You can even run Linux within. Ubuntu on FreeBSD, who would of thought. Can you run FreeBSD on Linux?
What I'm currently setting on my colocation box as I call them are cell's. Zones as if you wish to go Solaris'ly. Which by you can host bHyve, FreeBSD's native hypervisor in a separate jails giving you isolation. I host game servers publicly, so knowing they're restricted to their own cell, with a set amount of resources means I know my system is going to brick if something goes astray. As that too with ZFS allows me to backup real-time. Real-time migration and resource limiting, what more could you want?
There are other third party "container" attempts at containerizing FreeBSD. But in my opinion Jails are the bee-knees.
A feature I've never seen outside of the Unix world are: bectl and beadm. A dream, advance boot environment tools for when you really want to keep deep. Imagine compiling your kernel, rebooting only to find it panics. Those tools allows you to revert back to the OS to it's previous state, even jump into your newly built kernel without having to reboot. Magical.
Resources:
https://wiki.freebsd.org/Jails
https://wiki.freebsd.org/Containers
https://wiki.freebsd.org/LinuxJails
https://vermaden.wordpress.com/2022/03/14/zfs-boot-environme...