Column Headings Definitions for Transaction Report?

Yes,

When you are logged in on the back end as an administrator, you can navigate to the online help (link in the top right corner).  From the help, the help section on Donation reports (https://secure3.convio.net/njh/admin/AdminHelp?pagename=Admin_Donations_by_Transaction_Report) will have links to the various reports and includes a detailed description of the various fields included in the report.

Hope that helps, let me know if you are having any trouble viewing or finding the reports help that includes this info.

Cheers,

Adam