The backup infrastructure of Veeam Backup for Microsoft 365 consists of the following:
Backup proxy servers are auxiliary machines that you configure to conduct all read and write activities, route backup traffic, handle data compression and encryption and send email notifications.
Backup repositories are storage systems within the backup infrastructure where Veeam Backup for Microsoft 365 saves backups and backup copies.
Object storage is cloud-based or on-premises storage system that you employ to store your backups and backup copies as part of the extended backup repository storage system. Keep in mind that you can use Azure Blob Storage Archive access tier, Amazon S3 Glacier Instant Retrieval, Amazon S3 Glacier Flexible Retrieval and Amazon S3 Glacier Deep Archive storage classes only as a target for backup copy jobs.