[davidgaffer]

On Page Optimization is basically the effort which you put on the website and is clearly visible, Like:
" Optimizing the existing content
" HTML code corrections
" remove broken / dead links
" Add Meta / Alt Tags
" Add Google and XML Site Map
" Analytic Setup
It is very important that On Page Optimization is done correctly for a website as this educated search engine crawlers and spiders about the theme of the website and which keywords you are targeting to rank on. On Page Optimization is usually done once on the website however SEO Agency does On Page Optimization after every 3 months to keep the site fresh for Search Engines.

Off Page Optimization Is something which is done offsite and usually not visible on the website however results in pushing the ranking higher on search engines, it is a regular process and must be done ethically for better and long term results.
" Creation of New Pages
" Link Building Services
" Directory Submission
" Article Creation and Submission
" Classified Ad Creation and Submission
" Blog Post Message Creation and Submission
" Press Release Creation and Submission
" E-book Creation and Submission.