On Linux, keyring is a secure storage mechanism for sensitive information such as passwords, SSH keys, API tokens, or application credentials. It is managed by a service called GNOME Keyring (or a similar application if not using GNOME).
The keyring is encrypted with your password and automatically opens when you log in to the system with that password.
If you do not use a password when logging in (for example, you use auto-login or an account without a password), the keyring will not open automatically, and the application will ask you to enter the keyring password to access the data stored in it.