If you lose some of your most important files, emails or photos then its the most frustating moment because you have very/no chances of recovering them back. But now you have many Data Recovery softwares which can be installed on your computer in order to recover the accidently deleted files.
The files are recovered from your hard disks or memory cards and you have the option to recover deleted emails or mail attachments. Whenever you delete all the files from your computer they are still stored in the hard disk sectors and not completely erased unless you format the whole drive or when you add more data on your hard disk which replaces the older data.

These softwares try to detect the deleted data in the internal sectors of the hard drives and recover them if possible. To make sure you can recover the most of the data you need to make sure that you dont add any new data on the drives because that can replace the old stuff. Once the scanning is done by the recovery software you can get the preview of most files which can be recovered and you have the option to soft the files based on what files are easily recoverable.