Sometimes will detect a file which it cannot determine for sure whether it is a threat. When this happens, classifies the file as suspicious and sends it to quarantine.
The aim of quarantine is to keep suspicious files isolated from your system until it is determined whether they are really a threat. It is advisable to keep the option to automatically send files to our experts enabled. In this way we can provide an update as rapidly as possible.
For more information, refer to What can I do with files in quarantine?