Why is on-page SEO important?

On-page SEO gives the relevance to the quality of the content of your post/ website.
In general, What you write, how you write and how you present it to your audience defines On-page SEO.
This is an essential factor to increase Google ranking of your site.

On-page SEO helps search engines analyze your website and the content connected to it so that it can identify if a searcher's query is relevant to your site. Google is constantly updating their algorithm so that it can better understand a searcher's intent and deliver search results that meet that user's needs.

On-page SEO is important because it helps to search engines understand your website and its content, and also helps to identify whether it is relevant to a searcher query.
Search engines check your article coding language. It checks your on-page SEO parts like heading structure, image alt-text etc.
It's really helpful to earn a ranking in SERP (search engine result page)

In on page seo we have target right keywords that's best for seo