Search engine optimization (SEO) is often about making small modifications to parts of your website.
When viewed individually, these changes might seem like incremental improvements, but when combined with other optimizations, they could have a noticeable impact on your site’s user experience and performance in organic search results.
You should build a website to benefit your users and gear any optimization toward making the user experience better. One of those users is a search engine, which helps other users discover your content.
SEO is about helping search engines understand and present content.
Type of SEO:
1. ON PAGE SEO
2. OFF PAGE SEO
3. TECHNICAL SEO
source