Search engine optimization (SEO) is the practice of improving the ranking of information in search results. SEO is most often used to refer to the practice of improving the rank of websites in search engines, but also applies to searches on Amazon, Ebay, Etsy, LinkedIn, and other aggregation platforms.
SEO is one of the most powerful marketing tactics for improving the quantity and quality of your website traffic. Ranking higher in search engines (usually Google) is a way to reach an audience of people who are searching for exactly what you offer.
Although the term search engine marketing (SEM) is also common, SEM tends to refer to paid search tactics. SEO tends to refer to organic, unpaid search results.