Where did deleted files goes

I don't want a file so. I will delete it but isn't it get deleted. Nowadays we are using many types of storage device SD cards and pen drives their store the information in in kB,MB,GB,TB,PB,EB. But the question is where did the delete files

if you thinking that the files just simple delete. Then you are wrong
Actually the files or any thing you delete is just marks as empty and when you search a deleted file it will show you nothing because it mark empty by system but your file is their in system.
Once a photographer incidentally delete his photos folder the research manage to recover some files from that
Once you deleted a file a and you want it back you have write completly in system.