Content Marketing is marketing done for a great piece of content to make sure it can reach interested people (The medium could be TV, ad, print, Facebook Twitter, does not really matter)
Anything which brand creates to drive awareness, conversation or reach in any format of content (image,video, banner) called as content marketing..
Content Marketing is the star actor, Social media marketing is the movie. The star can also choose to appear in ads, concerts, etc or you can say content marketing is where you market your content everywhere in any form irrespective of medium of the channel.
Social Media marketing is restricted to only social..and which is subset of content marketing or I can say that content marketing is marketing by creating content and sharing it, social media can be marketing on any social media channel.Social Media Marketing only focuses on channels like Facebook, Twitter and other Social Platforms. So, if your company creates a great TV commercial and later shares it on Facebook then, making the ad is called content creation. Publishing the ad on TV and Facebook is called Content Marketing and finally only the part where you publish the video on Facebook is considered Social Media Marketing.
Social media marketing is also a vehicle that helps brands grab eyeballs while great Content is the Star sitting inside the vehicle. Without the star, no one cares about that vehicle.Also In social media marketing – you market your content only on social media networks or in other words you use only social media channels to market.