What is a domain? I will describe in an easy-to-understand manner.
A domain refers to the unique and specific name that characterizes a delimited section of the Internet, such as a website for example. For Internet users, a domain often appears in this form:
www.example.com
As an important part of a URL ( Uniform Resource Locators), a domain tells us where a resource is located in the structured hierarchy of the Domain Name System (DNS). The translation of a domain into IP addresses is done using this system. These are specialized web servers responsible for resolving names and IP addresses. This service works in the same way as directory inquiries: the user types the domain name www.example.com into the search bar of his web browser and the latter will send a request to the relevant server name. This is where the entry www.example.com will be loaded into the database and will pass the stored IP address to the browser. it is a basic WordPress Course Training.
Setting up a domain
Fully Qualified Domain Name (FQDN) is the full term for “domain”. An FDQN gives the exact position of a target computer in the hierarchical tree structure of the Domain Name System (DNS) and is composed of two parts: the computer name (Host-Name or IP address) and the domain. The following example shows the FQDN of a fictional email server:
mailserver.example.com.
The mail server part of the above address tells us about the name of the machine (Host-Name) and the example.com part about the domain, under which we will find the computer in question. The characters www are generally used as Host Names for the servers responsible for the exploitation of Web pages.
www.example.com.
It must be taken into account that the Fully Qualified Domain Name (FQDN), unlike commonly used Internet addresses, always ends in a dot. This is due to the hierarchical structure of the domain name system: the domains are distributed starting from the upper level, the so-called Root-Label.
Here is the structure from right to left of the domain cited as an example: Root-Label, extension (TLD), second-level domain (SLD) then third-level domain. In this way, the FQND of www.example.com contains four sections. In principle, domains can contain subdomains below third-level domains.
Root label
The first level of this tree structure is therefore called Root-Label. The Root-Label of an FQDN is defined as empty and does not appear on Internet user applications as a rule. Server name entries ( Resource Records ) should always show the full names of the domain and end with a dot after the extension: www.example.com.
Extensions (Top-Level-Domain)
If the Root-Label is empty, the extension will pass first according to this structure. Extensions are managed by Network Information Centers (NIC). One counts among the fields of action of a NIC the management of the names of servers as well as the attribution of the domains of the second level below the extension. The IANA ( Internet Assigned Numbers Authority ), one of the departments of the company for the allocation of domain names and numbers on the Internet, distinguishes two main groups of top-level domains: generic extensions such as .com or. info and national top-level domains such as .fr or .de. Subsets of generic extensions are sponsored by special interest groups or corporations. The registration of such a domain may be linked to special conditions or editions. Since the top-level domain is the last part of a domain, the synonym of "extension" has become widely used. For example, the .com ending corresponds to the top-level domain.
Second Level Domain (SLD )
The second-level domain is a freely selectable subdomain of the top-level domain. Still with the same example, “example” is the .com subdomain. The assignment of a second-level domain will always take into account the higher-level domains. The competent NICs for the commercial extensions are generally in charge of the accreditation of the private Registrar.
Third-level domain
Below these three top-level domains is a domain characterized as a third-level domain. This subdomain is to the left of the second-level domain in the fully qualified domain name ( FQDN ). This prefix on a domain name distinguishes the devices used because the World Wide Web ( www ) is only one web application among many. However, it remains the best known. The most used prefixes as third-level domains are www for web services, m for mobiles, and also mail, IMAP, or pop3for email servers. There are also different specific national indicators. The online encyclopedia Wikipedia is a good example. Here is how these specific domain names are structured: The English Wikipedia page prefixes are en. In addition, specific third-level domains may allow the use of an already existing domain name (such as the company name for example) depending on regional possibilities.
Third-level domains are often characterized by subdomains. But this term subdomain is not limited to third-level domains.