Site indexing is a very complicated process. I will give you
a brief, simplified explanation below.
A spider crawls your web page. The search engine algorithm analyzes it and gives it a rank for different keywords. Now your page listing is
ready for the Search Engine Results Page (SERP.)
If your page doesn’t have any links pointing to it, then it won’t show up in the SERPs. As time goes on and your page gains popularity, it
is listed higher up in the SERPs.
For example, if your page achieves a higher ranking, it could show on the first page of Google for a given query. If your page is new and has limited links, it could end up on page 100 of a search query.