Decentralized Social Media, also called blockchain-based social media, refers to social media platforms that use sources such as the blockchain to power themselves. Therefore, any activity by a user on said platform is not supervised by a large central overseer, such as those with centralized social media platforms like Twitter and Facebook.
In the case of Facebook and Twitter, revenue is generated by advertising content that is exposed to the user. These centralized social media companies also have much control over what a user posts and, as their main goal is profit, it is in their interest to advertise as much as possible to the user. This also gives them the ability to have a lot of power in what a user also digests. In essence, the user is the product to advertising companies rather than the social media platform being the product to the user.
With decentralized social media, users are given the freedom to use the platform in any way they see fit without many restrictions. There are guidelines the user must abide by of course, but these are not as strict as others given by the likes of Twitter or Facebook.
Another major difference from traditional social media compared with decentralized social media is that the user privacy is magnified and the ownership of their own data is completely theirs. This prevents the sale of user data to advertising companies or unknown third-parties which has been a major issue for Big Tech companies in recent years.
Despite this, decentralized social media does not come without its own problems. As more freedom is given to users, this can result in an increase in disinformation and the posting of content which can support hate-groups or marginalize certain groups of people.
With less moderators on these platforms, information such as this can spread very quickly with no-one fact-checking or controlling the information. Also, due to the platform being powered by the blockchain, there is a greater risk of an outside attack. In theory, one person could possibly take over the entire network, allowing them to edit any information and data they see fit. This would of course be a major blow to any decentralized platform.
Probably some of the best known decentralized social media platforms include Mastodon (very similar to Twitter), Minds (seen as an alternative to Facebook & YouTube) and Karma (a mobile-only version of Instagram).