what is on-page in seo?

[Gina]

On-page optimization : On-page optimization means making small modifications
in your website which have a noticeable impact on your site's user experience and performance in organic search results.

On-page optimization includes :
Page Load factor
Meta Description tag
ALT tags
H1 tags
URL structure
Internal linking strategy
Content
Keyword density
Site maps, both XML and HTML
RSS Feed
Usability and accessibility

Avoid common on-page SEO mistakes such as:

Duplicate content
URL variants of the same pages
Off-site images and content on-site
Duplicate title tags

Avoid spammy SEO tactics such as:
Hidden text
Hidden links
Keyword repetition
Doorway pages
Mirror pages
Cloaking