On-Page SEO refers to all the things that you can do ON your website to help you rank higher, such as page titles, internal linking, meta tags & descriptions, etc.
On-Page Search Engine Optimization:
1] Page Titles: Your page titles are one of the most important SEO factors on your site. Each of your pages & posts should have its own unique title, which includes the main keywords for that page.
2] Meta Descriptions: Many people forget to include meta descriptions for their pages. These descriptions are an important place to include relevant keywords for your content, as these are used within the search results when your page is listed.
3] Meta Tags: For each of your pages, you can include a set of keywords in the form of meta tags. These should be all the relevant keywords of your content, which you will have researched previously.
4] URL Structure: Including search engine friendly URLs for each of your pages is highly recommended, as these bring better crawling. Shorter URLs seem to perform better in search engine results, however that is not the only factor.
5] Body Tags (H1, H2, H3, H4, etc.): When writing your articles, you should break up your content into smaller sections & paragraphs to make it easier for people to read. These sections can be given heading, which is where H1, H2, H3, H4, etc. tags are used.
6] Keyword Density: Including relevant keywords throughout your content is very important, as it helps search engines work out what your content is about. However, try not to excessively repeat and overuse keywords just for search engine robots. This can lead to your site being banned from search engines.
7] Image SEO: Using images within your content is a great way to make your site more visually appealing and break up boring chunks of text. You can utilize these images to help improve your site SEO.
You can also include Alt Text and Descriptions for your images, making them even more useful with SEO.
8] Internal Linking: Placing links to your other website pages, is a great way of improving your site and used properly, internal links can be a useful weapon in your SEO arsenal. Not only does it make it much easier for your visitors to navigate around your site and find all of your content, but it also ensures that your site gets properly crawled allowing the search engines to find all of your pages. It also helps to build the relevancy of a page to relevant keywords and phrases, whilst also helping to increase the Google PageRank of your pages.