SEO can be somewhat tedious and time consuming.
In some cases it can take as much time or more than it does to build an actual website. Search engine codes are added to your website. Special “keywords” ( not quite as important as they used to be ) are generated to attract Google and others. All sorts of unique steps are taken that are specified by the individual search engines. Text is laid out in a certain manner so your website moves up the search engine food chain. All this and more goes on behind the scenes so your website makes its way to the first page of the search engines. And yes, if you’ve ever heard of algorithms, the search engines use them.
Quality content, or text, is also very important.
Google can tell when you have copied content from another website. Or that your content (what you are saying on any given page) makes sense and is well written.
Another very important aspect of SEO are “backlinks” – how many quality websites are linking to YOUR website because your website has such great content.