Deleting files from the computer just makes it invisible from the explorer but what really happens is that the entry of the file is removed from the allocation table thus making the file to be recovered by the use of data recovery software. Data recovery software search the free memory space for the existence of the deleted file and finds the file and recovers it. 

But if you want the file not to be recovered the deletion will not work for you as the file can be located. But if you want the file to be completely unrecoverable then you have to shred the file using the specialized software called data eraser tool. This tool performs the basic function of file deletion i.e. removal of file from allocation table but additionally fills the file with garbage value thus making the file recovery software not to recover this file. Thus, if you want a file not to be accessible by anyone after you have worked on it. You can wipe data using the data eraser tool. But you must be cautious while using this tool because if you delete an important file then you will not be able to recover it. Thus it will lead you to a permanent loss. Therefore it is always advised to keep the backup of the file you delete using the data eraser tool.