What is the difference between "Configuration Stored on XBlock Fields" Vs "Configuration Stored on this Model"?

The “Cofig store” field on the “Add LTI Configuration” page in the admin portal can be set to two values - “Configuration Stored on XBlock Fields” and “Configuration Stored on this Model”.

Can any one help with how both differs? When to use the first one and when to use the other?

Thank you.