The monthly backup includes all transaction files created during the previous month, as well as all transactions that closed or expired in the previous month.
It will also include any transactions where you have manually checked the Include in Backup checkbox (e.g., active transactions you want to be included).
The transactions are organized in folders by property address and include everything associated with a transaction: Documents, notes, checklists, emails, and activity history. Docs are included in their original format, while notes, emails, checklists, and activity history are in plain text format which is compatible with all computers.
The backup is in the universal ZIP file format and can be opened using the unzip option built in to most computer systems. You can also use 7-zip to open the downloaded backup file if your computer's default unzip option isn't working: