Dynamic IP Address
Check this if your ISP uses dynamic IP address assignment.

Static IP Address
Use this if your ISP has given you a static IP address.

Auto-configure Hostname from this IP
Select this option if you want kppp to set the hostname and domain for your machine after making a connection (rarely used).

Default Gateway
Use this if you want pppd to use the default gateway for your machine.

Static Gateway
Use this to specify a gateway.

Assign the Default Route to this Gateway
You should leave this on unless you specifically know otherwise.