Denial of service is literally translated as "Denial of Service". System administrators use the abbreviation DoS. It happens that users send a large number of requests to an Internet resource that it does not have time to process, and the incoming information is overloaded. Attackers can disable even the strongest and most powerful servers. If you look at it from a technical point of view, then each site is hosted on a server. It, in turn, can belong to the hosting provider or the site owner. The Internet resource has its own limitations on the amount of memory for storing incoming and posted information on it. The limits depend on the amount of traffic and the capacity of the hard disk. How do they manage to get such a high level of traffic? But now you can even order a ddos attack, for example here https://ddos-stress.cc
Every day, the server is exposed to a large number of different requests. Most of them are completely empty and don't make any sense. If the server does not have special protection, it processes and sends a response signal to each of them. This leads to an overload of incoming traffic and the server itself. For a narrow-band channel, only a couple of hundred requests become a threat, and if we are talking about high-frequency requests, this figure increases by hundreds of thousands.
A large flow of requests from outside leads to a slowdown in the site, and then to its stop (as an option-fighting with competitors, and you can even buy a ddos attack). When hosting a site on the same hosting, third-party resources are also affected, which also store their data on the same hard disk. Situations like DoS often occur on the Internet. For example, it can be news videos or posts posted on the official website of Zvezda or a TV channel. A DoS attack is a peaceful phenomenon and is not associated with illegal actions.
It can also be used for DDOS attacks on competitors or enemies.