Don’t rush to memorize the definition: Does an audited protocol have to be safe?
In 2016, The DAO was attacked due to a reentrancy vulnerability. Ethereum responded with a hard fork, while the original chain that did not fork continued as Ethereum Classic (ETC).
If the code is changed after an audit, or the version actually deployed differs from the audited version, the audit’s conclusions may no longer apply.
When you see a new protocol offering yields significantly higher than similar ones, first check whether it has been audited, whether the team is public, and whether the contract can be upgraded at will.
The Ethereum network associated with $ETH is one of the earliest public blockchains to support general-purpose smart contracts.