What is the blockchain? I had this question myself, so I did a bit of research to find the answer. Wikipedia says, "A blockchain, originally block chain, is a growing list of records, called blocks, that are linked using cryptography. Each block contains a cryptographic hash of the previous block, a timestamp, and transaction data (generally represented as a Merkle tree)." What does this mean? It means a blockchain is a bunch of bits of data, linked to each other by cryptography, which is basically using math to secure data. Also, each block has a math-shortened version of the block before it and other data.
I was rummaging the Internet for no reason again when I found Holochain. It claims to be a new way to run applications, without having to run what is a full node on other blockchains. They claim, "Since users are hosts, as more agents use an app, more hosting power and storage becomes available. The load gets lighter!" (Emphasis mine.)
As I was watching videos on the blockchain to educate myself on the subject, I learned about consensus. For normal blockchains, such as the Bitcoin blockchain, this means every node on the network has to have essentially a full copy of the blockchain. This is totally not sustainable for average users on mobile phones. This is one of the differences of the Holochain. Each user has their own blockchain, not a copy. Using a technology known as Distributed Hash Tables, or DHT for short, there are other copies of your data elsewhere, but not everywhere. That way, if you posted to social media from your phone, and you go offline, then people can still view your posts.
Holochain is also different in that it's not currency-based. However, there is a cryptocurrency already on the platform in use by Holo, the flagship hosting provider for Holochain. Instead, Holochain is centered around applications. These may require arbitrary data to be stored in blocks, rather than tokens, senders, and recipients.
In short, Holochain is the hash-chain app network of the future. It's built for apps. It does away with super-nodes that centralize what isn't meant to be centralized. It isn't built for cryptocurrency, but it supports it anyway. There's a follow-up question I'll answer another time: is it Web 3.0 ready?