There are four different domain name levels in the web;
The first one is: TLD - Top Level Domains. It is the highest level domain section in the system. It is the part of a domain name which comes after dot ".".
The second one is: SLD - Second Level Domains. It is the part of a domain name which comes before "."(dot).
The third one is: gTLD - Generic TOP Level Domains. This part called gTLD is not related to any country. gTLD includes domain name extensions " .com / .net / .org ". All of those extensions have different meanings but in order to use them, you don't have to be authorized, so it means that it is not an official-serious topic eventually. While the extension ".net" means communities in the network that are trying to develop some useful technologies or creating something interesting, the extension ".com" means business, which means if your major aim on this website is to make money, you can use the extension ".com". Additionally, there is the other one called ".org" and it means non-profit companies or charity.
The fourth one is: ccTLD - Country Code Top Level Domain. If A domain name extension is registered by a country, that domain extension name takes place in this category called "ccTLD". They are reserved for those countries, and it doesn't matter whatever happens. They are completely owned by that country.