A user account grants a person access to the data in a Google account with a web browser. User accounts are for people connecting with a web browser. The service account gives applications remote access to the data in a Google account.

Google Service Accounts

A service account is a special kind of Google account and authentication that is used by programs such as ETL+ rather than a person. ETL+ uses a service account to authorize access to your Google Sheets. The service account's roles control which Google resources ETL+ can access.

  • A service account is identified by its email address, which is unique to the account.

  • Service accounts use public/private RSA key pairs rather than passwords. The RSA key required to access a service account is created by Google and saved in a .json file.

Differences between a service account and a user account

Service accounts differ from user accounts in a few key ways:

  • Service accounts do not have passwords, and cannot log in via browsers or cookies.

  • Service accounts are associated with public/private RSA key pairs that are used for authentication.

For more see https://cloud.google.com/iam/docs/service-accounts