Wirebook › Glossary › Overwrite
What does overwrite mean?
In one sentence: Saving new data on top of old data, which finally destroys what was there before.
A little more
Deleting usually just forgets where a file was. Overwriting is what actually destroys it: new data is written into the same blocks, replacing the old ones and zeros.
"Shredder" programs overwrite a file on purpose before deleting it. On SSDs and phones, the drive's own tidying and encryption do the job more reliably than shredding does.
It's a bit like… Recording a new song over an old cassette: the old song is gone where the new one now sits.