Google’s primary job is to surface the most relevant, trustworthy, and authoritative information for any given search while also matching the intent of the search. They do this by way of their ever-evolving algorithm, which ranks the expertise, authoritativeness, and trustworthiness of every URL on the internet based on roughly 250 different factors.
SEO is the practice of optimizing your website and content against each of these factors to give your website the best chance to be highly ranked on searches relevant to your business. SEO is often confused with search engine marketing (SEM), but the goal of SEO is to acquire organic traffic. SEM includes strategies to acquire both organic and paid traffic.