Technical SEO is a term used for SEO techniques that are mainly related to the technical aspects of your site. For example, site loading speed, your site's overall look, user experience, user-friendliness, etc. If your site loads slowly, your site will not be ranked high on search engines even if you have done on-page SEO and off-page SEO correctly. Your site also needs to be user-friendly and easy to navigate for a better user experience.