When you delete an item from a SharePoint document library or list, it isn’t immediately removed from SharePoint. Deleted items go into the site recycle bin for a period of time (30 days). During that time, you can restore the items you deleted to their original location. If you're using SharePoint Online, you can even view and restore items that were deleted by someone else, as long as you have edit permissions on the item.

Here is a step-by-step guide: https://support.office.com/en-us/article/restore-items-in-the-recycle-bin-of-a-sharepoint-site-6df466b6-55f2-4898-8d6e-c0dff851a0be#ID0EAADAAA=Online