As the name implies, on-page SEO tactics will be done on the main site. This means, activities within the website are focused on for optimizing. Search engines will focus on activities like meta tags, titles, keyword and even speed of the page among other internal structures.
Off-page on the other hand will focus on the external elements like backlinks, social media promotions and other. Both on-page and off-page are what determines ranking of websites on the SERPs.
Off-page on the other hand will focus on the external elements like backlinks, social media promotions and other. Both on-page and off-page are what determines ranking of websites on the SERPs.