Report Designer Field Descriptions

Is there any sort of guide that lists what the Report Designer fields are, in the reports of ServiceDesk 7.5?  I'm seeing some reports that might be useful (that I could modify), but I'm not sure what all the fields are on the left hand side (Data column).  Some are easy to figure out, but I'm not familiar with all the terminology yet.  I'm just looking to pull basic reports at this point.

Thanks!

ServiceDesk 7.5