SEO (Search Engine Optimization) is the process of affecting the visibility of a website or a web page in a search engine’s unpaid results – often referred to as “natural,” “organic,” or “earned” results.
You can of course purchase ads from search engines which will show your web page on the first page of search results for certain keywords. This is not what SEO is about. SEO is about the normal, natural, and unpaid portion of the search results. It attempts to make your website more visible to search engines by paying attention to some details on your own website when the website is being developed.