TLDs are Top Level Domains and are divided into two groups:
- ccTLD (country code Top Level Domain) referring to countries, nations and geographical areas such as .it, .de, .fr, .uk or .eu (e.g. registro.it).
- gTLD (generic Top Level Domain) are generic, such as .net, .com. or .org. (e.g. fao.org)
For more details: http://www.icann.org/