Blockchain

A blockchain is a shared distributed database or ledger between computer network nodes. A blockchain serves as an electronic database for storing data in digital form. The most well-known use of blockchain technology is for preserving a secure and decentralized record of transactions in cryptocurrency systems like Bitcoin. The innovation of a blockchain is that it fosters confidence without the necessity for a reliable third party by ensuring the fidelity and security of a record of data.

Understanding Blockchain
Blockchain records and distributes digital information without allowing editing. A blockchain is the basis for immutable ledgers, which cannot be changed, deleted, or destroyed. Blockchains are distributed ledger technology (DLT).
The blockchain concept was first presented as a research study in 1991, before Bitcoin. Since then, blockchains have been used to create cryptocurrencies, DeFi apps, NFTs, and smart contracts.

Decentralization
Imagine a corporation with tens of thousands computer server farm that stores client account information. This corporation owns a warehouse that houses all of these computers and controls all of their data. This creates a single failure point. What if the power fails? What if it loses Internet? Suppose it burns down. What if someone deletes everything with one keystroke? Data is corrupted or lost.
A blockchain allows database data to be shared across multiple network nodes. This creates redundancy and protects the fidelity of the data stored there.
Any attempt of modifying records on one database will no affect other nodes of the chain, preventing a bad actor from doing so. If a user tampers with Bitcoin's transaction record, all other nodes can cross-reference and find the culprit. This system establishes a clear timeline. No network node may change data this way.
Information and history (like cryptocurrency transactions) are irreversible. A blockchain can hold a list of transactions (such with a cryptocurrency), legal contracts, state IDs, or a company's stock inventory.
To validate new blocks, a majority of the network's computer power must agree. Blockchains are protected by proof of work (PoW) or proof of stake to prevent malicious actors from confirming bad transactions or multiple spends (PoS). These mechanisms facilitate agreement without a single leader.
Due to Bitcoin's decentralized blockchain, all transactions may be examined transparently by utilizing a personal node or blockchain explorers. Each node's copy of the chain is updated as new blocks are added. You could follow Bitcoin if you wanted.
When exchanges were hacked, Bitcoin holders lost everything. Although the hacker is anonymous, their Bitcoins are traceable. If some of the stolen Bitcoins were spent, it would be known.
Only the owner can decode a record to expose their identity, using a public-private key pair.

Blockchain Safety
Blockchain accomplishes decentralized security and trust in several ways. New blocks are stored sequentially and chronologically. They're always appended to the blockchain's "end." Once a block is put to the blockchain, it's difficult to change its contents unless a majority of the network agrees. Each block contains its own hash, the previous block's hash, and the timestamp. A mathematical function creates hash codes from digital data. Changing the information alters the hash code.
A hacker who controls a blockchain node wants to steal cryptocurrency from everyone. If they changed their copy, it wouldn't match others'. When everyone compares their copies, this one will stand out, and the hacker's chain will be discarded as invalid.
To succeed, the hacker must control and alter 51% or more of the blockchain copies such their new copy becomes the majority copy and the agreed-upon chain. Such an attack would need a lot of money and resources because all the blocks would need new timestamps and hash codes.
Due of the scale and growth of many bitcoin networks, the cost would be overwhelming. This would be expensive and futile. Network members would notice such severe blockchain changes. The network members hard fork to a new, unaffected chain. This would cause the targeted token's value to collapse, rendering the attack futile since the bad actor now controls a worthless asset. Same if a malicious actor attacked Bitcoin's new fork. Participating in the network is economically more rewarding than opposing it.

Blockchain and Bitcoin
When Stuart Haber and W. Scott Stornetta developed blockchain in 1991 to prevent document timestamp tampering, blockchain didn't have a real-world application. Until Bitcoin launched in January 2009.
Bitcoin uses blockchain. Bitcoin's developer, Satoshi Nakamoto, introduced it as "a novel peer-to-peer electronic cash system with no trusted third party"
Bitcoin utilizes blockchain to record a transparent log of payments, but blockchain may store any amount of data points immutably. This includes transactions, votes, goods inventories, state IDs, home deeds, and more.

Blockchain and Banks
Blockchains are seen as disruptive to the finance sector, especially payments and banking. Banks and blockchains are different.