A blockchain is an network of computers that collaborate to agree on certain facts. It acts as a tamper-proof storage layer that everyone can trust. This network of computers can run software stored in the blockchain and check one another’s results for veracity before adding the result to the blockchain. This enables secure computation to take place across the network.
A blockchain is at the heart of the DFINITY world computer
Lots of computers around the world not controlled by a single organization sort of work together to secure and agree on a ledger of transactions.
Blockchain is a tamper-proof database. It's a way of storing data in such a way that it cannot possibly be manipulated. And we often see blockchain paired with a giant international computing network that allows individuals or organizations to add things to this database according to very certain rules, and allows everyone else in the world to see what's in that database.
A blockchain is basically a global ledger that everybody can trust. If you want to keep records, if you write it on a piece of paper and maybe store it somewhere, that might work okay if you trust the person who keeps it and it's in a very secure safe or something, but that sort of thing won't scale. A blockchain lets many people around the world record things and in a trustworthy way. Everyone can look at the ledger they create together and be confident that it's the truth.
Blockchain to me is a very abused term. To me, it's just a distributive computing construct that's used to bring typically a large network to agreement.
This one of the fundamental ways I think about it, that the reason you have this tamper-proof distributed ledger is that you can execute computations across thousands and thousands of nodes. So then, no matter what happens later, that computation can be trusted.
Blockchain is a distributed data structure. What is a data structure? Any structure that you can store value in a computer. So, like an array, a list, is a data structure. A tree structure is a data structure. Blockchain is also a data structure that is composed of blocks.
Right now if compare the state of where we are in the blockchain space to the internet we're somewhere in the 1980s where we're still talking about the lowest layers of the stack, of the tech stack. So asking "What is a blockchain?" is kind of similar to asking ... Asking, "How does a blockchain work?" is kind of similar to asking, "How does email work?" Where now we all know applications and we can tell you press send and a an email address here and there. We're much, much lower on the stack than that. And I think that's why people are giving different answers because everyone kind of sees it from a different perspective, and there's no mass-market applications right now that make it really ... That allow us to really feel what the blockchain is.
Blockchain has two primary properties. The first property is called persistence, where if you put something on the blockchain, it stays there forever. And the other one is what's called liveness, where no one can prevent you from putting things on the blockchain. Once we have these two properties, persistence and liveness, that enables a whole host of applications, one of which is a cryptocurrency. But more generally, a blockchain enables a decentralized computer, it enables asset management, and so on. But fundamentally, a blockchain really is just a way to store information so that the information is persistent, information cannot be removed from the blockchain, and the blockchain is live in the sense that everyone can keep writing to the blockchain. There's no way to prevent people from writing to the blockchain. It literally is a sequence of blocks. Each block is just a blob of data. So it literally is just a sequence of blobs of data, where each blob depends on the previous blob. And when a blob is created, the persistence property means that that blob can never be removed.
A blockchain is an authenticated data structure which is used by a distributed set of participants, usually a P2P network to come to agreement on a common view of the world. The work could be, for example, the history of messages. In particular, it would be the ordering of the messages within this history. Of it could be the state of a state machine, for example.