docs: --privileged docs completeness, consistency
As discussed in
@@ -43,7 +43,19 @@ Pass down to the process N additional file descriptors (in addition to 0, 1, 2).
**--privileged**
-Give the process extended Linux capabilities when running the command in container.
+Give extended privileges to this container. The default is *false*.
+
+By default, Podman containers are
+"unprivileged" and cannot, for example, modify parts of the operating system.
+This is because by default a container is only allowed limited access to devices.
+A "privileged" container is given the same access to devices as the user launching the container.
+
+A privileged container turns off the security features that isolate the
+container from the host. Dropped Capabilities, limited devices, read/only mount
+points, Apparmor/SELinux separation, and Seccomp filters are all disabled.
+
+Rootless containers cannot have more privileges than the account that launched them.
+
**--tty**, **-t**
