Search engine optimization (SEO) involves optimizing websites to increase their visibility in search engine results. The goal is to help websites rank higher in search engine results pages through both on-page techniques, like keyword optimization of titles and content, and off-page techniques like link building. SEO is important for driving traffic to websites from search engines since most internet users find websites through search engines like Google. While SEO requires an ongoing effort, it can be an effective way to promote websites and businesses in a cost-effective manner if done properly.