Keychain is a feature of macOS that securely stores passwords, account numbers, and other confidential information for your Mac, apps, servers, and websites1. You can use the Keychain Access app on your Mac to view and manage your keychains and the items stored in them1. Keychain can also sync your passwords and other secure information across your devices using iCloud Keychain1. Keychain can be used as a password manager in macOS to help you keep track of and protect your passwords.
References: 1: Manage passwords using keychains on Mac
(https://support.apple.com/guide/mac-help/use-keychains-to-store-passwords-mchlf375f392/mac)