Access Point: select if you want to run your IPCop as Access Point. Please note that this option may not be selectable, depending on installed WLAN card.
SSID: Service Set Identifier to use.
Disable SSID broadcast: select if you want disable broadcasting the Service Set Identifier, please note that this is not a real security feature.
Automatic start: select if you want to automatically start WLAN after booting IPCop.
Encryption: select which encryption to use. Unless running a public WLAN AP you should use WPA.
Use Antenna: currently untested, use with care.
Channel: which WLAN channel to use. Choose wisely to not interfere with any neighbours.
Tx Power: could work for those cards that offer it.
802.11n (Draft-N): may (or may not) give you some extra speed. Do NOT expect to reach those 300 Mbit values that are advertised!

Passphrase: will be used together with SSID to generate PSK. Must be between 8 and 63 characters long.
WPA Version: can be 1, 2 or 1+2.
WPA Algorithm: can be 1, 2 or 1+2.
Loglevel: regulate the amount of information logged and viewable through Logs -> System Logs -> Section: WLAN AP.

WEP is considered unsecure. Use only if you know what you are doing.