What are the goals/specialization/actual use of each? FreeBSD: I always got the impression this was trying to be full modern UNIX but non-linux NetBSD: I gues

What are the goals/specialization/actual use of each? FreeBSD: I always got the impression this was trying to be full modern UNIX but non-linux NetBSD: I guess this is for older/less powerful computers based on comments here? OpenBSD: ???Security??? Dragonfly: a schism over threading, but FreeBSD?