What is the difference between On Page SEO and Off page SEO?

On-page SEO refers to the factors you can control on your own website, Off-page SEO refers to the page ranking factors. 
Meta description, HTML code, title tags, and alt tags, that’s the foundation for on-page SEO. On-page SEO refers all the measures that can be taken directly within your website to improve its position in the search rankings. This includes those basic tactics listed above, but also takes into consideration things like overall content quality, page performance, and content structure.
While on-page SEO refers to the factors you can control on your own website, off-page SEO refers to the page ranking factors that occur off your website, like backlinks from another site. It also includes your promotion methods, taking into account the amount of exposure something gets on social media. Backlinks, domain authority and social promotion comes under it.
On-page and off-page SEO work together to improve search engine rankings. By working on what you can control today—producing quality content that is supported by high-quality on-page SEO—you’ll be well on your way to earning backlinks, improving your domain authority, and controlling your off-page SEO.