On-page and Off-page are both part of SEO techniques. On page techniques increase the visibility of a webpage and make it search engine friendly. it includes URL optimization, H1 tag, image optimization, w3 validation, keyword density, content optimization.
And, Off-page techniques generates quality and quantity of backlinks which increase search engine results. It includes forum posting, social bookmarking, directory submission, article marketing, classifieds posting, blog posting.