Indexation refers to the process by which search engines like Google collect, parse, and store web pages in their massive databases, known as the search index. Once a page is indexed, it becomes eligible to appear in search results when users query relevant terms. Without indexation, your content is essentially invisible to search engines.
For a page to be indexed, it first needs to be discovered by a crawler (like Googlebot) and then deemed valuable and unique enough to be added to the index. Factors influencing indexation include the quality of your content, internal linking, external backlinks, and technical SEO elements like a well-structured XML Sitemap and proper use of noindex tags.
You can check the indexation status of your pages using tools like Google Search Console. If a critical page isn't indexed, it's crucial to investigate potential issues such as crawl blocks (e.g., in robots.txt), noindex directives, or content quality problems. Ensuring proper indexation is the fundamental first step for any SEO strategy.