Introduction

A Blockchain is a distributed database that is shared among the nodes of a computer network and protected by crytography.

• It stores information in blocks that are then linked together via cryptography.
• Different types of information can be stored on a blockchain, but the most common use so far has been as a ledger for transactions.
• It guarantees the fidelity and security of a record of data and generates trust without the need for a trusted third party.
• Decentralized blockchains are immutable, which means that the data entered is irreversible.

Unlike traditional database instead of storing data in tables, a blockchain structures its data into chunks (blocks) that are strung together.

• Each block in the chain is given an exact time stamp when it is added to the chain.
• Blocks have certain storage capacities and, when filled, are closed and linked to the previously filled block, forming a chain of data known as the blockchain.
• All new information after that freshly added block is then again compiled/grouped into a new block which will then also be added to the chain.

A blockchain is a globally shared, transactional database. This means that everyone can read entries in the database just by participating in the network.

• If you want to change something in the database, you have to create a so-called transaction which has to be accepted by all others.
• The word transaction implies that the change you want to make is either not done at all or completely applied.
• While your transaction is being applied to the database, no other transaction can alter it.

Smart Contract

Smart contracts are simply programs stored on a blockchain that run when predetermined conditions are met. They are typically used to automate an agreement's execution so that all participants can be immediately sure of the outcome without any intermediary's involvement or time loss. - IBM

It is a self-executing set of instructions that is executed without a third party intermediary. Smart contracts are a set of instructions which when placed on a blockchain are self-executing pieces of code not run by any centralized intermediary.

They are written in code. Smart contracts are typically paired with some type of oracle to get some information about the real world, when smart contracts are paired with an oracle they're called hybrid smart contracts.

Chainlink is a secure decentralized modular oracle network used to bring data into your smart contracts and also make some type of external computation.