Memo is both a protocol and a front-end application. The protocol works by writing transactions to the Bitcoin Cash blockchain. Client applications can read these transactions to see the activity on the network.
With current social networks, users do not control their data and can have their accounts removed without reason. The blockchain is more than an uncensorable way to send money, it’s an uncensorable way to store data. Memo is an experiment leveraging the blockchain’s data storing capabilities.
Each action is stored on the blockchain in an OP_RETURN transaction – whether it’s posting a memo, following someone, or liking a post. You can also include a tip (it is on-chain after all). Additional actions are intended to be added later.