What is the Keychain App on a Mac and how is it used?
Keychain Access is a macOS app that stores your passwords and account information and reduces the number of passwords you have to remember and manage.
When you access a website, email account, network server, or other password-protected item, you may be given the option to remember or save the password. If you choose to save the password, it’s saved in your keychain so you don’t have to remember or type your password every time.
Because Keychain Access securely stores and retrieves your user names, passwords, and other information, you can make individual passwords more complex and difficult to break. This can make your individual accounts more secure.
Important: To ensure that passwords and other data stored in your keychain are secure, make sure to set up a login password for your computer. See Change the login password.
You can store any type of sensitive information in Secure Notes.
You can also use Keychain Access to manage certificates, which are issued by trusted organizations to validate websites, digital documents, and other web-based materials.
Keychain Access works in collaboration with iCloud keychain, which lets you share keychains with your other devices. To create and manage your iCloud keychain, sign in to iCloud with your Apple ID. See the Apple Support article Frequently asked questions about iCloud Keychain.
Source: https://support.apple.com/guide/keychain-access/what-is-keychain-access-kyca1083/mac