An online company creates a relationship between your desktop company file and the online application or service you subscribe to.
Your Intuit Account can have multiple companies so that you can easily exchange data between all of your company files and the online applications or services you're using.
When you sync your data for the first time using Intuit Sync Manager, an online company is automatically created for the company file you have currently open in QuickBooks.
Once the online company is created, you can pick this company to work with your applications and services so that you don't have to upload your data again. You can also invite coworkers to use your applications online.
For applications that work with QuickBooks data, Intuit Sync Manager will always create the online company for you. But for applications that do not use QuickBooks data, you will be prompted to create the online company yourself during the subscription sign up process.