Difference between On Page Optimization and Off Page Optimization

On Page Optimization-  On page optimization is the important part of SEO.In On page we work on meta tags, title tags, head tags, keyword, SEO friendly URL, content of website. In short words we work on our website for our web promotion

Off Page Optimization-  Off page optimization is the second part of SEO. In off page we work on link building techniques like forum posting, blog commenting in SEO blog, directory submission, article submission and reciprocal linking.In short words we use other's website and forums for our web promotion.

So both are important we can not promote our website with only On page  or Off page. We need to work on both for good ranking