It is exactly same as SEM but rather than being on search engine it is on social media platform.
It is the same basic aggressive marketing of your content with money which is spent on advertising your own content on various social media platforms which show your advertisement on related pages so you get more traffic on your site.
But it does cost alot of money as compared to simple Social Media Optimization and you definitely need to have top-class content to show off otherwise it'll not be worth it.
SOCIAL MEDIA MARKETING
It is a powerful way of generating traffic and attention towards your site.