--- en_US.ISO8859-1/books/faq/book.xml	(revision 42051)
+++ en_US.ISO8859-1/books/faq/book.xml	(working copy)
@@ -5889,6 +5889,21 @@ 
 	    it serves to firewall the process off from processes owned
 	    by other users.  The user ID is also used to firewall
 	    off on-disk data.</para>
+
+	  <para>In addition to process and userid sandboxes offered by
+	    the &unix; operating system, &os; provides the &man.jail.8;
+	    feature, a secure, fast implementation of <ulink
+	      url="https://en.wikipedia.org/wiki/Operating_system-level_virtualization">
+	      operating system-level virtualization</ulink>. This
+	    allows a single &os; computer to run one or more guest &os;
+	    system images with their own users, IP addresses, and
+	    processes. Unlike &man.chroot.8;-based sandboxing,
+	    processes are permanently confined to the jail they were
+	    started in (including those owned by the jail's root user),
+	    and cannot affect processes in other jails or the host
+	    system. While the &man.jail.8; feature is unique to &os;, it
+	    is similar to Solaris Zones, AIX Workload Partitions, and
+	    Linux Containers.</para>
 	</answer>
       </qandaentry>