When you delete a file on your computer, only a reference to the location of the file is deleted. In other words, the file system simply "forgets" that the file exists.
But the actual data, the 0's and 1's, still remain on the disk.
Let's explain what happens in simple terms: The specified files will continue to remain there until your system writes new files to its track disk where the old ones were. During this period software may be used recoverys for the recovery of "deleted" files.
However, file shredding applications like Permadelete ensure that the files you delete cannot be recovered. If you want to know more, you can read here how Permadelete works.
Note: You will need .Net Framework 4.5 to run the application, and you can download it from here.
You can download the latest one version (0.6) of Permadelete from the link below
https://apps.microsoft.com/store/detail/permadelete/9MVHV99VWL64
Check out the project on GitHub