An audit is a full assessment and review of the code. Audits are performed pre-deployment since all the contracts on the blockchain are final and immutable. During an audit, the developers have the opportunity to fix the discovered problems and add comments to those that are left in the code on purpose. Smart contract audit is one of the most important security criteria for a particular project. A significant role in the quality of the audit is played by the auditor company that conducts it. Learn more on the website of HashEx, one of the world's most influential auditors.