These pages provide a simple PHP class to parse, store and query the Public Suffix list.
about the public suffix list
Top Level Domains (TLDs) include the familiar country codes such as .uk, .fr; US codes such as .edu, .gov; the old international codes sucha s .org, .com; and the growing number of further level codes such as .name, .tv. They are adminstered centrally an it is easy to get a list of them.
However, many countries have a second tier of naming, for example, .co.uk and .ac.uk in the United Kingdom. The domain name system does not include a standard way for these to be updated, but they are important, for example to know whether you should be blocking all of .co.uk or just badsite.co.uk for malevolent behaviour.