DAWs (digital audio workstations) edit by using metadata. Suppose you have an audio file that is 2 minutes long. You start using it in the application. The application notes "we have 2 minutes of audio, taken from the start of this file". Now if you "delete" the last minute of the file, nothing is done to the file, but the "metadata" inside the DAW now says "we have 1 minute of audio, taken from the start of this file".
If you then copy 20 seconds from the middle of that section, the DAW refers to this with metadata essentially saying "20 seconds of audio starting 20 seconds into this file".
Nothing is ever done to change the contents of the actual file.
ps. I write a DAW for a living.