Most often, this is accessed via the Tor browser, so most of the sites on the darknet are in a pseudo-domain.onion. Pseudodomain means that in fact there is no such domain on the Internet, but they can be accessed inside the darknet.
For example, if you enter the address in a normal browser, an error will be displayed because DNS servers do not know how to handle this domain. And if you enter the same address into the Tor browser, the HiddenWiki – Wikipedia window for the darknet will appear. There is nothing forbidden in it, it just tells you where you can go if you have entered the darknet for the first time:
Onion sites are usually hosted on virtual hosting sites, which are easy to start or just as easy to change, if necessary to preserve anonymity. For the same reason, some links do not work in the darknet, because the hosting sites where these sites were hosted have closed or moved to a new address. Therefore, link catalogs are popular on the darknet — special thematic collections of sites from which users choose the right ones.
HiddenWiki is also an example of such a directory.
Search engines are there too, but they’re not as cool as Yandex or Google. The fact is that in the darknet a lot is hidden from indexing and is only available by direct link. Examples of search engines from there are TORCH and Seeks.