DNS - (Domain Name System) - a hierarchical distributed naming system that allows the identification of Internet services and resources, allowing end-user devices to use Internet routing and communication services to reach these services and resources. And now in human terms.
Computers do not understand the concept of an address in the way we understand it. The page You are visiting does not have the address ww4.it, only a specific sequence of numbers. For google.com, at the time of writing this article, it is the address 142.250.75.14, while google.co.uk hides under 142.250.203.19. So - in short - DNS is a translator of addresses that are digestible by humans into addresses that computers understand. When registering a domain with any operator, You must indicate on which DNS servers it will be maintained and indicate the IP addresses of computers that will provide such a service.
At one time, it was agreed to use one protocol (IPv4), in which addresses consist of four 256-digit numbers. For some reason, the own address of each computer was specified as 127.0.0.1. When the number of computers began to grow rapidly, it was agreed that the addresses 192.168.* and 10.* would be assigned to shared networks. In 1984, it was agreed that each country would have its own national domain (.uk, .de, .jp, .au) and the first version of universal domains (.com, .net, .org) was introduced, as well as domains for specific institutions in the United States (.mil, .edu, .gov). In 2000, another set of universal domains was introduced (including .biz, .info, .aero, .pro). Each country has a main domain registrar who is responsible for maintaining the top-level domain and commercial registrars (including GoDaddy, OVH).
You have set up a DNS server, but Your company has several branches of services. For example, You are a transport company and You run a workshop, warehouse, refrigerated warehouses and a trailer wash. You do not want to register a dozen or so domains for them, so You place them in subdomains of Your domain. Let's assume that Your main domain is ww4.biz, so in Your configuration file You enter these industries and the IP address of the computer on which the page of a particular industry will be located. For example, transport.ww4.biz, You will assign the workshop the address truck-workshop.ww4.biz, the ambient warehouse the address ambient.warehouse.ww4.biz (and here we already have a third-level subdomain), and the low-temperature warehouse - frozen.warehouse.ww4.biz. All 4 pages will be launched on Your server in Your server room. Only the trailer wash site (clean-hgv.ww4.biz) will be on a separate machine, connected to the booking system.
How does DNS work? It is similar to standard map reading. If we want to go to the Prime Minister at 10 Downing St, London SW1A 2AB, Great Britain, we first have to be in the UK, then get to London and only then look for Downing Street, and when we are there - the address of building no. 10.
In the case of our transport company, to find the address of workshop.ww4.biz, a computer somewhere in the world will check the address of the ww4.biz domain and the server that serves it will ask: do You know where I can find the address of workshop.ww4.biz? This - if the service is properly constructed - will respond with the IP address and the browser will connect to the address indicated, with the question: can You show me the workshop site?
In the DNS service, You also configure the address of the server that will serve e-mail. But more on that in the next article.
If You have any questions - feel free to contact us.