When you log in to FireCloud after your account has been activated, you will be asked to allow FireCloud to have offline access. This is because FireCloud obtains Google access tokens when you log in to FireCloud. These access tokens last for one hour.
FireCloud also obtains and stores Google refresh tokens to obtain new access tokens. The acquisition of an access token through the use of the stored refresh token is the requested "offline access." We would like to acquire new access tokens on your behalf so you do not need to manually log back in.
For example, you may have a long-running job that requires a new access token after one hour. We would like to request a refresh token to generate a new access token so your job will continue running.