The grid-file specifies the sites and related information for a grid. Instead of listing all of the grid sites on the command line to site_submit you can specify a grid-file with --grid-file. Similarlly you can specify a --grid-file to summarize_condor_log to provide category information and suppress removed sites. For more information on usage see those files.
Blank lines and lines beginning with '#' are ignored.
Remaining lines list grid sites, one per line. Each line contains multiple fields seperated by commas. Whitespace at the beginning and end of a field is trimmed. At some point there may be escaping using the comma-seperated value format or backslashes. At this point no such escaping exists; avoid using double quotes or backslashes as their behavior may change.
The first field is the Globus resource name. The canonical form will be "hostname.example.com/jobmanager-batchname". The second field is the number of simultaneous jobs to send to the site. The third field is the "category". Categories are used to organize results in the reports. One use for the category would be to create a "known bad" category to seperate sites that are not expected to be working.