Is the address under which your website will be on the Internet. Detailed and easy to understand You can learn more about domains on www.jakpsatweb.cz or All about hosting.

Tier 2 domain is for example blueboard.cz

A Tier 3 domain is for example hosting.blueboard.cz

A 3rd tier domain is also called a subdomain. There is no charge for it (but it is possible that some hosting sites may charge something for it, these are not quality hosting sites)