It contains 2 types of files: e$S and log files.
The e$S files are actually normal QuarkXPress files which were saved prior to a QuarkXPress crash. You can usually change the file extension of the e$S to QXP and thus reopen the latest version of your document.
The log files contain detailed debugging information as to where the source of the crash was, and is automatically included in the files that are sent via technical support.
Topic 184420, last updated on 17-Mar-2021