On Page and Off page both are equally important so whenever you are doing SEO you have to perform this both task perfectly.
On Page Optimization: On page optimization is On site optimization you have to make changes on your site like Meta Tag Creation, H1 tag, Alt Tag, Internal Linking, Content Optimization etc.
Off Page Optimization: In off page optimization you have to submit your site link/Content to other sites. You can submit your content/link to Directory Submission sites , Social Bookmarking Sites, Article Submission sites this all are the off page activity. For more detailed information about On page and off page activity check below list
Here is some of On page and Off page Steps.
Off Page Optimization: