On page SEO is a technique which we do on a site and it optimize individual webpage to get higher and more traffic in search engine. It refers to optimization of both content and HTML source code of page. It helps to get more traffic on your website.
Off Page SEO is a technique which we do outside the webpage. It helps to increase traffic on site and optimize site performance in search engine. It is about getting a backlinks from other sites to higher the rank on search engine results page.