Search Engine Optimization is a tactic use to optimize content such as web pages, blog post or landing pages to be shown on the search engines like Google. In order to offer a level play field, search engines have created a formula (Algorithm) to give priority to the most relevant content for users in the Search Engine Results Pages (SERPs). The relevance is given by evaluating many elements in your content like keywords, page title, meta description, image tags, internal link structure, inbound links and more. Also, Google has been giving priority to websites with better structure, design, security (SSL), and mobile optimization.
Always develop your content with your audience in mind and optimize it for the search engines. Avoid using bad practices such as Keyword Stuffing, Hidden Text or Links which can result in the removal of your website from search engines forever.