This is not the latest version of this documentation, for the one that is upto date, please see the latest version (2.6.9)
APN & PIN
The WWAN connection usually doesn’t require any sort of configuration as the setup is done automatically. If your service provider requires an APN that needs to be setup or if your SIM card that is inserted has a PIN you can specify them here.
PDP Type
If your ISP is finicky about IPv6 or you're having issues multi-homing IPv6 with your main WAN interface in any way, you can always choose IPv4 only as the PDP type. This will force the WWAN interface to only use IPv4.
IPv6 Prefix Delegation
If your ISP provides you with an IPv6 prefix delegation that you want to use on your LAN, you can enable this option, if you don't want your LAN to use IPv6, you can disable it.