How to create a language version on site subdomains?

Question

Web development

Hello! I am making a landing page in 2 languages, Russian and English. For myself, I chose this way: I create 2 identical sites, just the language of the content on one site is Russian, on the other English. I found this option
"Creating language versions on subdomains of a site can also be implemented in two ways:
1. configuring the server to process a subdomain as a language parameter (within one site)
2. copying the site to physical folders of subdomains (within several sites)
, but I didn’t understand how it’s done.Can someone tell me?That is, I don’t want to buy 2 separate domain names, but I want there to be one domain, but when I click on the "EN" button, it transfers to the site in English