SharePoint keeps track of changes and updates of files in your library. You can see the changes that were made (created, edited, deleted) and when (18 hours ago, yesterday, last week). You can view only activity on individual files and documents, or your whole library.
See the file activity in a document library
Open the document library
Select Open the details pane
Scan the Activity section to view the latest activities for your files
To close the details pane, select Open the details pane again
Note: When a file is selected, you may see a preview and file properties in the details pane before the file activity. When more than one file is selected, you can edit the properties of the selected files. When no files are selected, you will see activity on the library.