Linux, Unix. For someone who is asking what it is, simpler response is "just a distro".

Except it really isn’t, distros usually refer to different distributions of Linux but not different types of operating system.

I usually say to layman that they are different forks of unix from many years ago.

OpenBSD and Linux have a lot of the same tools to be sure but they are different enough that you have to learn them both if you are administering them.