The three letter word SEO is described as all the activities performed which effect the ranking of the websites on different search engines. SEO includes on site & off site and many other activities.
White Hat SEO | How to Rank #1 in Google? | Do I need SEO?
Digital Marketing is a wide range of online marketing activities, which are used to approach your customers to provide, educate, make them aware of and sell them your products and services.
Social Media Marketing | Facebook Marketing | Google AdWords Marketing