describe the mood of the text in 3 words: "Service accounts provide an identity for unattended applications, such as batch jobs, worker processes that dispatch messages in a queue, or resource-monitoring agents. By using a service account, you allow these applications to run without user interaction. Also, if the application accesses a resource, you can use Cloud Audit Logs to trace that access back to the service account that the application uses.

Service accounts are also useful for applications in which a user authenticates with a custom authentication scheme, then indirectly accesses Google Cloud resources. These applications can confirm that the user is authenticated and authorized, then use a service account to authenticate to Google Cloud services and access resources. To help trace that access back to the user, the application can write a custom log entry each time a user accesses a resource, and you can correlate the custom log entries with Cloud Audit Logs.

Unlike users, service accounts can't authenticate by signing in with a password or with single sign-on (SSO). Instead, service accounts support a different set of authentication methods. The following sections describe how to choose between them. You can also use the following diagram to help you choose an authentication method:"