Книга: Iptables Tutorial 1.2.2
The chapter you have just read basically gave you a brief overlook of all the different scripts that are available with this tutorial and the basic idea that they are trying to bring across to you. Hopefully it has been able to explain something at the very least.
The next chapter will discuss some different graphical user interfaces that are available for iptables and netfilter. This is far from a complete listing of all the different interfaces available, but as you can see, there are quite a lot of othem. These interfaces mostly tries to simplify creating iptables scripts for you, and for simple setups they are more than enough most of the time. At other times, you may have higher and more complex needs and you must have to write your own script none the less.