[Atheros]

Social media is a service where people who know each other in real life communicate mostly about things happening to them personally.

Online Publishing is process by which people, who largely don't know each other in real life, publish their content for others to consume via an online service.

A Link Aggregator is a service where people publish links to outside web services and users vote to establish the ranking on the aggregator.

The only reason any of this is debatable is because old social media sites like Facebook, Instagram, and Twitter stopped being Social Media and switched to Online Publishing and people are having trouble updating their vocabulary.