What is the difference between social media and digital marketing?

Digital marketing is an umbrella term for the targeted, measurable, and interactive marketing of products or services using digital technologies to reach and convert leads into customers and retain them. The key objective is to promote brands, build preference, engage with customers and increase sales through various digital marketing techniques. It is embodied by an extensive selection of service, product, and brand marketing tactics, which mainly use the Internet as a core promotional medium, in addition to mobile and traditional TV and radio.

Under the Digital marketing Umbrella, the major  activities are search engine optimization (SEO), search engine marketing (SEM), content marketing, influencer marketing, content automation, campaign marketing, and e-commerce marketing, social media marketing, social media optimization, e-mail direct marketing, display advertising, e–books, optical disks and games, and any other form of digital media. It also extends to non-Internet channels that provide digital media, such as mobile phones (SMS and MMS), callback and on-hold mobile ring tones. The fundamental concept in digital marketing is based on the inbound marketing approach or generally it's called customer centric approach.

Hope it is clear now, for instance – again under the big umbrella there are many persons and Just one person is social media marketing.

Put simply: 

Digital marketing is the utilization of all digital marketing channels to promote brand awareness (television, internet, radio, digital billboards, social media, etc.). Social Media Marketing is the utilization of only social media to promote brand awareness and market products and/or services.

Social media is one part of digital marketing 

just diference of awairnessssss and popple responsible behave and attitude

agree with a great twice answer above

Question already asked few times. Social media is a part of digital marketing. Digital marketing is all your presence online.