The default column file is a text file which allows you to assign friendly names to properties.
This file looks very much like the names section of IDQ files.

You tell IS the location of your default column file assigning a value to the entry DefaultColumnFile found in the registry key.
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\ContentIndexCommon

you will probably have to create the entry.

The value of the key will be c:\temp\MyProperties.extention

MyProperties.extention will look like this:

[Names]
department =d1b5d3f0-c0b3-11cf-9a92-00a0c908dbf1 "department"
dateexpiry =d1b5d3f0-c0b3-11cf-9a92-00a0c908dbf1 "dateexpiry"
BookTitle = 00020329-0000-0000-C000-000000000046 urn:schemas.microsoft.com:fulltextqueryinfo:xmlfilter:book/title
Author= 00020329-0000-0000-C000-000000000046 urn:schemas.microsoft.com:fulltextqueryinfo:xmlfilter:book/author
ISBN= 00020329-0000-0000-C000-000000000046 urn:schemas.microsoft.com:fulltextqueryinfo:xmlfilter:book/ISBN

Using the default column file will allow you to use these properties in your queries without having to use the DefineColumn statements, and give you Friendly 
Name in the IS MMC, properties folder.