Blockchain (blockchain) is a distributed ledger technology that records every transaction on a decentralized network without the need for an intermediary. Each "block" contains transaction data and is linked to the previous block via cryptographic hash, forming an immutable "chain." Bitcoin was the first blockchain (2009). Ethereum expanded blockchain with smart contracts. In Vietnam, the 2025 Digital Technology Law recognizes blockchain as a foundational technology for digital assets.

DeFi (Decentralized Finance) is an ecosystem of financial services operating on blockchain without banks or intermediary institutions. DeFi includes: decentralized exchanges (Uniswap, PancakeSwap), lending/borrowing (Aave, Compound), staking, yield farming, and stablecoins. Total Value Locked (TVL) in DeFi reached $200B+ in Q1/2026. Users interact with DeFi through crypto wallets (MetaMask, Coin98) connected to smart contracts.

NFT (Non-Fungible Token) is a unique token on the blockchain representing ownership of a digital asset: images, music, videos, game items, domains, or certificates. Unlike Bitcoin or ETH (where each unit is identical), every NFT is unique. NFTs are most popular on Ethereum (ERC-721), but also exist on Solana and Polygon. NFT applications are expanding from art/collectibles to RWA, ticketing, and digital identity.

What is a stablecoin?

A stablecoin is a type of cryptocurrency designed to maintain a stable value, usually pegged to 1 USD. There are 3 types: (1) Fiat-backed — backed by real USD (USDT, USDC) — the most common; (2) Crypto-backed — backed by over-collateralized crypto (DAI); (3) Algorithmic — uses an algorithm to adjust supply (FRAX). Stablecoins are the primary "currency" in DeFi and crypto trading. In Vietnam, investors often use USDT for value storage and P2P trading.

What is a smart contract?

A smart contract is a self-executing program stored on a blockchain that automatically enforces programmed terms when conditions are met — without the need for an intermediary. Example: a lending smart contract automatically disburses funds upon receiving sufficient collateral and automatically liquidates if the asset price drops below a threshold. Ethereum was the first blockchain to support smart contracts (2015). Smart contracts are the foundation of DeFi, NFTs, DAOs, and all Web3 applications.