You have files that have been quarantined by Symantec Endpoint Protection (SEP) on a local computer, and have been directed to manually submit them via the online submission form rather than from within the product interface.
Note that for suspected missed malware, it is usually not necessary to submit files that are already detected and quarantined by Symantec products. Please see the Connect article Symantec Insider Tip: Successful Submissions! for additional recommendations on what to submit and what not to submit. For suspected False Positives, see Submit false positives detected by Endpoint Protection.
To gather files to submit
Note: This document only covers submitting files from SEP clients, not from a legacy standalone Central Quarantine Server (CQS) which is now past its End of Life.