Welcome back to the 60-Day Web3 Journey.
If you’ve been following along, you know what we’ve covered so far. Day 1, I introduced why I’m learning Web3 in public — to transition into Developer Relations and help non-technical people understand blockchain. Days 2–4, we broke down the fundamentals: what blockchain is, why Bitcoin was revolutionary, and how it challenged traditional money. Days 5–7, we went deeper into Ethereum — the programmable blockchain — and learned about wallets, gas fees, and why Layer 2 solutions exist to solve Ethereum’s scaling problems. Day 8, we understood smart contracts and dApps (decentralized applications) — the actual code that powers everything. And Day 9? We got our hands dirty. We deployed our first real smart contract on Sepolia testnet, felt the transaction cost, and saw how code lives permanently on a blockchain.
Now comes the moment where it all clicks.
You just deployed a smart contract on Ethereum and saw how code can live on a blockchain. Now comes the real question: what are people actually doing with these contracts?
The answer: they’re building an entirely new financial system. It’s called DeFi — Decentralized Finance — and it’s where smart contracts stop being abstract and become the backbone of how people trade, lend, borrow, and earn money without banks.
This is Day 10 of your 60-day Web3 journey. Let’s see what you’re about to enter.
What Is DeFi, Really?DeFi is finance without a middleman. Instead of a bank holding your money, a smart contract does. Instead of a broker matching your trade, an algorithm does. Instead of a lender deciding if you qualify, code does.
Here’s the core idea: take every financial service you know — trading, lending, borrowing, investing — and rebuild it as code that anyone can use, anytime, from anywhere.
That’s DeFi.
The key difference from traditional finance:
Traditional Finance:
DeFi:
Let me walk you through the three biggest types of DeFi protocols right now:
1. Decentralized Exchanges (DEXes) — Swap Tokens InstantlyA DEX is like a vending machine for crypto. You put in one token, you get another token out. No human operator. No waiting. No fees to a company.
The most famous is Uniswap. As of December 2025, Uniswap has over $5.7 billion locked in it — that means people have deposited $5.7B in tokens across thousands of trading pairs. Here’s how it works:
No middleman. No trading desk. No commission. Just code.
Uniswap v4 (their newest version, launched mid-2025) hit $1 billion in TVL in just 177 days and has processed over $1 trillion in annual trading volume. That’s real money moving through smart contracts.
2. Lending Protocols — Earn Interest, Take LoansWhat if you could deposit your crypto and earn interest — without a bank? That’s Aave.
Aave is the biggest lending protocol in DeFi. As of mid-2025, it has over $60 billion in deposits and $29 billion in outstanding loans. It controls roughly 60% of the entire DeFi lending market.
Here’s the flow:
If you want to borrow, you do the reverse:
No credit check. No bank manager. No waiting for approval. Just math: if you have collateral, you can borrow.
In August 2025 alone, Aave saw its TVL grow by 55%. In Q2 2025, the protocol generated $122 million in fees. Real money. Real usage.
3. Yield Farming — Stake Tokens, Earn RewardsThis is the newcomer to the DeFi toolkit, and it’s wild.
Yield farming is when you lock up tokens in a protocol and earn rewards in return. Sometimes the rewards come from protocol fees. Sometimes they come from newly minted tokens the protocol gives you as an incentive to provide liquidity.
Example: You deposit ETH and USDC into Uniswap’s liquidity pool (the vending machine from section 1). For providing that liquidity, you earn a share of trading fees plus UNI tokens as a bonus. That’s yield farming.
It sounds simple, but it’s powerful: DeFi protocols can incentivize behavior they want (liquidity provision, borrowing) by paying users with newly minted tokens.
Why Does This Matter? (2025 Context)DeFi isn’t theoretical anymore. Here’s what’s actually happening:
Scale:
Adoption:
Institutional Money:
This isn’t a niche anymore. This is infrastructure.
Deep Dive: Watch ThisIf you want a structured breakdown of everything DeFi, YouTuber faixal_abbaci released a comprehensive 32-minute DeFi Masterclass (December 2025) that covers:
Remember your SimpleStorage contract from Day 9? It stored a number permanently on the blockchain.
That’s the mechanism behind DeFi. Aave, Uniswap, all of it — they’re just more sophisticated smart contracts doing exactly what yours did: storing data and executing rules when triggered.
The difference:
But the principle is identical: code running on a blockchain, with no middleman, doing the job that bankers used to do.
What’s the Catch?DeFi is powerful, but it’s not without risk:
These are real risks. But as of 2025, millions of people believe the upside (financial access, high returns, no middleman) outweighs the downside.
Hands-On: Try It YourselfWant to see DeFi in action? Here’s the simplest starting point without spending money:
Notice that there’s no login page, no terms and conditions, no “sign up” button. It’s just code. Open to everyone. Available 24/7.
That’s the revolution.
What Happens Next?You now understand:
Tomorrow (Day 11), we’ll talk about NFTs — which, like DeFi, are powered by smart contracts but solve a completely different problem.
But before you go, here’s a thought: if DeFi lets you trade, lend, and borrow without permission, then what’s stopping someone from doing the same thing with digital art, game items, or concert tickets?
That’s NFTs. That’s Day 11.
Key TakeawaysDeFi 101: Decentralized Finance was originally published in Coinmonks on Medium, where people are continuing the conversation by highlighting and responding to this story.