What is the difference between a Databricks user and a service principal, and when should I use each one?
A Databricks user is a unique individual who has access to the system, represented by an email address. Users can interact with the Databricks workspace, notebooks, and other assets. They are typically used for data scientists, engineers, and analysts who need to access and work with data directly.

A service principal, on the other hand, is a service identity for use with jobs, automated tools, and systems such as scripts, apps, and CI/CD platforms. Service principals are represented by an application ID. They are typically used for programmatic access to the Databricks workspace, such as running jobs, managing clusters, and accessing data objects. Service principals are useful when you need to automate tasks or integrate with other systems, as they provide a way to authenticate and access Databricks assets without requiring a user account.

In summary, you should use a Databricks user for individual users who need to interact with the Databricks workspace, and a service principal for programmatic access and automation tasks.