To safeguard your QuickBooks data against accidental loss, create regular backups of your QuickBooks company file. The backup contains everything you need to re-create your company file and QuickBooks environment, including all of the QuickBooks files (templates, letters, logos, images, and so on) related to your company file.
In case of accidental loss or damage, you can use the backup file to restore your company data. A backup file also includes a transaction log (.tlg file) which Intuit Technical Support can use to recover transaction data if damage or loss occurs. Unlike a portable file, a backup file is very large and cannot be emailed. It is not recommended as a means of moving company data, unless you have a new computer and need to move all of your related files as well. The backup file is saved with a .qbb extension.
To email or move your company data, create a portable company file. A portable company file is a compact version of your company file, small enough to be sent by email or saved to portable media. Use a portable company file whenever you need to copy your company data to another location or send it to another person.
Unlike a backup file, a portable file contains only a compressed version of the company file financial data—it doesn't contain related files such as letters, images, templates, and so on. It also doesn't contain a transaction log (.tlg file) and is not always the best option for a synced company file. The portable file is saved with a .qbm extension.
Portable company files overview
Back up company files overview