BSS mode
Also known as infrastructure mode, this is used when associating with an access point, through which all traffic passes. This mode is the default.
IBSS mode
Also known as IEEE ad-hoc mode or peer-to-peer mode. This is the standardized method of operating without an access point. Stations associate with a service set. However, actual connections between stations are peer-to-peer.
Host AP
In this mode the adapter acts as an access point (base station) for other cards.
monitor mode
In this mode the driver is able to receive packets without associating with an access point. This disables the internal receive filter and enables the card to capture packets from networks which it wouldn’t normally have access to, or to scan for access points
Взято отсюда: http://www.openbsd.org/cgi-bin/man.cgi?query=ath&sektion=4
