AdvOnLink and AdvAutonomous (radvd in IPv6) ?????

Hello,

I installed a Linux box as a router.
In the /etc/radvd.conf, there are two variables (AdvOnLink and
AdvAutonomous) associated with each prefix that the router must
advertise. The value of these variables can be on or off.

When both variables are on (AdvOnLink=on and AdvAutonomous=on),
it is clear. The following example tell to the hosts that go to
autoconfiguration process that they must generate an IPv6 address
from the prefix (AdvAutonomous=on) and that they must put the prefix
in the prefix list (AdvOnLink=on). So two hosts that got configured
in a network where this prefix is advertise can send packet to each
other without passing through a router.
prefix 2001:8b0:67:4::/64
{
AdvOnLink on;
AdvAutonomous on;
};


What is the meaning of the other possibilities ????? In witch case it
is necessary to use the other possibilities ?????
- AdvOnLink=on and AdvAutonomous=off ????????????
- AdvOnLink=off and AdvAutonomous=on ????????????


Help will be very appreciate,
Thank you very much.

Eric.