Blockchain Basics for Beginners: From Bitcoin to Smart Contracts

Recently I have heard a lot about crypto, blockchain, Bitcoin, Ethereum, smart contracts, DeFi, dApps, DAOs, NFTs, Web3, etc.

I wanted to learn more, but many tutorials assumed prior knowledge, making it confusing for a true beginner.

I eventually found a comprehensive 16‑hour video tutorial on FreeCodeCamp (link: https://www.youtube.com/watch?v=M576WGiDBdQ) and took notes from a complete beginner’s perspective.

Physical money and our spending are controlled by entities such as governments and banks. Decentralized networks can address these issues by providing transparency, freedom, and security.

Blockchain is a type of database where information is stored in linked blocks. The ledger is shared across many computers (nodes), so there is no single record; multiple copies make it nearly impossible to hack, and all records are visible to everyone.

Unlike traditional databases, blocks in a blockchain are immutable; once data is written it becomes a permanent record. New data is added by creating a new block that links to the previous one, forming an ordered chain.

Because a blockchain is decentralized, there is no central authority controlling what can happen.

Bitcoin was one of the first protocols to use blockchain. It is a cryptocurrency that enables peer‑to‑peer transactions, with all transaction records stored on the blockchain. Like physical money, the supply of Bitcoin is limited.

Ethereum is another blockchain protocol whose native token is Ether (ETH). Beyond decentralized currency, Ethereum allows developers to build decentralized applications (dApps) and decentralized autonomous organizations (DAOs).

Ethereum also supports smart contracts—code that automatically enforces the terms of an agreement. Smart contracts on Ethereum are written in Solidity.

The advantage of smart contracts is that parties do not need to trust each other; the code executes the agreed terms without reliance on a third party.

Bitcoin’s smart contracts are not Turing‑complete, whereas Ethereum’s are, giving them broader functionality. To access external data, smart contracts use oracles, which provide off‑chain information in a decentralized manner.

Chainlink is a popular decentralized oracle network that feeds clean external data to blockchains, enabling hybrid smart contracts that incorporate off‑chain inputs.

dApps are decentralized applications typically composed of multiple smart contracts.

These notes reflect my current understanding; I will continue to learn and discuss further.