DEFI FUNDAMENTALS
What is a Vault in crypto?
"Vault" is one of the most overloaded words in DeFi. It can mean a technical standard, an automation layer, a simple deposit contract, or something else entirely depending on which protocol you are reading about. This guide untangles those meanings and explains how pigi.finance sidesteps the confusion.
The Ambiguity Problem
Ask ten DeFi users what a "vault" is, and you will get ten different answers. In the crypto space, the term is genuinely ambiguous — it describes very different concepts depending on the protocol and the context:
- An ERC-4626–compliant smart contract (a precise technical standard)
- An automation layer built on top of DeFi protocols (e.g., a yield optimizer that auto-compounds rewards)
- Any DeFi mechanism for depositing tokens to earn yield (a casual, protocol-agnostic term)
- An automated trading or investment strategy that manages capital according to some logic
This isn't just a naming quirk — it creates real confusion when comparing protocols. A "vault" on Yearn Finance works very differently from a "vault" on Maker, and both work differently from a lending pool on Aave that some dashboards also label as a vault.
The word "vault" tells you very little on its own. What matters is the mechanismbehind it: how does it accept capital, what does it do with it, and how does it return yield?
The Technical Definition: ERC-4626
In the most precise sense, a vault is a smart contract that implements the ERC-4626 standard — a specification published in 2022 that defines a common interface for yield-bearing tokens on Ethereum and EVM-compatible chains.
The standard solves a real engineering problem. Before ERC-4626, every yield protocol invented its own deposit/withdraw interface. Integrating ten protocols meant writing ten different adapters. ERC-4626 gives them all a shared API:
The core mechanic is a shares model. When you deposit, you receive shares that represent a proportional claim on the vault's total assets. As the vault earns yield, its total assets grow — so your shares become worth more over time, even though the share count stays the same. When you withdraw, you redeem shares for the underlying assets plus any accumulated yield.
Where you'll see it: Most modern yield aggregators, lending wrappers, and auto-compounding protocols on Ethereum have adopted ERC-4626. Examples include Yearn V3 vaults, Morpho vaults, and Aave's aToken wrappers.
Vaults as Automation Layers
The second common meaning of "vault" refers to a smart contract that automates a strategy on top of another protocol — most often by auto-compounding rewards that would otherwise require manual claiming and reinvesting.
Imagine a liquidity mining program where a lending protocol distributes governance tokens as incentives. Without automation, a user would need to periodically:
- Claim the reward tokens
- Swap them for the underlying asset
- Redeposit into the pool
An automation vault does this automatically on behalf of all depositors, typically several times per day. This converts the quoted APR into a higher effective APY and saves users on gas costs by pooling the harvesting transactions.
An automation vault's value comes from removing the operational burden of active yield management. It earns the same yield as the underlying pool, plus the compounding effect.
Where you'll see it: Beefy Finance, Yearn Finance, and Convex are prominent examples. They layer automation and fee-sharing on top of base protocols like Curve, Aave, and Compound.
Pools: A Related Concept
The term "pool" has similar breadth. Generally it refers to a smart contract where users deposit capital, with the most common usage being liquidity pools in Automated Market Makers (AMMs).
In an AMM like Uniswap, a pool holds two assets (say ETH and USDC) and uses a mathematical formula to allow anyone to swap between them. Liquidity providers deposit both assets into the pool and earn a share of trading fees proportional to their contribution.
Like "vault", the word "pool" is used loosely across DeFi:
- Liquidity pools in AMMs (Uniswap, Curve, Balancer)
- Lending pools (Aave, Compound) where depositors fund a shared reserve that borrowers draw from
- Insurance pools where capital backstops risk exposure
- Staking pools that aggregate validator stakes
At the smart contract level, a pool and a vault can look structurally similar — both accept deposits and issue claims on pooled assets. The difference is usually in theirpurpose: pools are typically designed around enabling trading or lending, while vaults are designed around maximizing yield for depositors.
How pigi.finance Uses the Term "Vault"
Rather than restricting "vault" to only ERC-4626 contracts, pigi.finance uses the term broadly to cover every structured on-chain vehicle that accepts capital and generates yield — regardless of the underlying contract design.
On pigi.finance, a Vault includes:
ERC-4626 vaults
Smart contracts implementing the standard share/asset interface, typically used for auto-compounding yield strategies.
Non-ERC-4626 vaults
Older or custom yield contracts that predate the standard or chose a different interface, such as Yearn V1/V2 yVaults.
AMM liquidity pools
Pools from protocols such as Uniswap, Curve, or Balancer, where depositors earn trading fees and liquidity mining rewards.
Stability pools
Pools such as Liquity's Stability Pool, where depositors provide a backstop and earn liquidation gains and protocol incentives in return.
On pigi.finance, every yield opportunity — whether it's technically an ERC-4626 vault, a liquidity pool, or a stability pool — is a Vault. One consistent term, no guessing required.
When a new mechanism appears that doesn't fit existing vocabulary, the Vault concept absorbs it naturally. Capital in, yield out, rules defined — that's a Vault, whatever the underlying contract calls itself.
Related reading
Understanding DeFi Yield Sources
Lending, liquidity mining, staking, RWAs and more — every category of DeFi yield, explained.
Aave TVL: Two Ways to Measure
Why pigi.finance and DeFiLlama report different Aave TVL numbers — and what each one actually answers.
CAGR vs APR vs APY
Three numbers, three different questions — and how to compare DeFi yields without mixing them up.