A contract that holds state and delegates its logic to a separate implementation address, allowing the logic to be replaced without changing the address users interact with.
Why it matters
Upgradeability is what makes a bug fixable after deployment — and what makes “the code is immutable” untrue for most deployed protocols. Whoever can point the proxy at new logic can change what the contract does to funds already held in it.
What you can check
The proxy pattern is visible on-chain: the implementation address, the admin address, and whether the admin is an externally owned account, a multisig, or a governance contract behind a timelock. That chain of control is the actual security model.
Not advice. Definitions are for understanding, not instruction. Nothing here is financial, legal, tax or security advice.