A file association is the information available to Windows internally, which associates a particular file extension with a particular Windows application. An example most people will be familar with is the association between the '.doc' extension and Microsoft Word ™.
When a file association is created, the user can double click on a file name which ends with the relevant extension, and have the appropriate application start up with the file already opened. Usually this would be done when viewing the contents of the containing folder (using Windows Explorer), or when a shortcut to the file has been created on the desktop.
Another feature is that, typically, the file icon shown in Windows Explorer will resemble the associated application icon.
Use Graphic Accounts to open files with '.acc' file exension
When this option is checked, clicking on an Graphic Accounts accounts file, or a shortcut to the file, will launch Graphic Accounts and load the clicked file name.
Use Graphic Accounts to open files with '.bgt' file exension
When this option is checked, clicking on an Graphic Accounts budget file, or a shortcut to the file, will launch Graphic Accounts and load the clicked file name.