When executing scans (on-demand or as part of real-time protection), some programs or files may have been categorized as threats. At that time, they were removed from the disk location where they were stored, placed in quarantine, and modified so that they could not pose a threat to your computer. There may be files which fall into this category, but are not malicious. It is up to individual users to research these files to make this determination. Upon entry to the History module of Malwarebytes Anti-Malware, you are presented with the Quarantine page, as shown below.

This page allows the user to view the contents of this quarantine, and to restore or delete files if desired. Quarantined files are shown in a table format, with pertinent information presented to help you determine which action needs to be taken. Each file listed has a select checkbox in the leftmost column. Check the checkbox to restore or delete the selected file. Please note that the Restore and Delete buttons are greyed out until one or more files are selected. If you wish to apply the same action to all quarantined items, select the checkbox in the table header and click Restore or Delete.

Please be aware that quarantined items which are not deleted or restored will continue to be visible here until action is taken.