SEO aims to get people to your website by aligning their search queries with your content. So, SEO is considered an organic search tactic, meaning that the results are earned, not purchased. You pay to optimize your website for search, but not for each individual click that goes to your website.
Google Ads – often called PPC (Pay-Per-Click) is still related to search, but you basically bid on keywords and pay a fee to Google every time someone clicks on your Ad in the search results.