Why is a site with "www" available, but not without "www"?

Question

Domain name market

Moreover, when you access the site from other Internet access providers, everything works regardless of "www"

Answer 1

Check your .htaccess, it might be in there.

Answer 2

nginx config for example:

server_name www.example.net example.net;

Answer 3

And record for it in general is In dns?

Answer 4

In your DNS settings, add an A or CNAME record for your domain.
Then, in the web server settings, specify that the new third-level domain is processed in the same way as the existing one.