Search engine optimization or SEO is the process of increasing visits to your site by posting helpful and relevant content to what the users are looking for. It totally depends on "the Google algorithm" and its strict rules or guidelines.
In a nutshell, people trust Google’s search results and this is why they have such a large market share.
With this trust comes a belief that if the user finds you on the first page of Google you must be one of the main companies that provide this service or product with high quality, so he will never hesitate and will immediately reach you out.