What Is SEO?
SEO — search engine optimisation — is the work of making your website easy for search engines to understand and useful for the people searching.
How search engines work
Search engines discover pages by following links and sitemaps, store them in an index and then decide which pages best answer a search. If a page can't be crawled or its content is only loaded after user interaction, it may never be considered.
Technical, on-page and content
Technical SEO makes pages crawlable and fast. On-page SEO gives each page a clear title, description and heading structure. Content answers real questions better than competing pages. All three work together.
What SEO can and can't do
SEO improves your chances of being found for relevant searches. It doesn't guarantee positions, and results take time. Anyone promising a fixed ranking should be treated with caution.