You can delete an audio region with files recorded in the current session, and you can delete an audio region with files that are imported from an earlier session.
Select the audio region, and press the Delete key.
A dialog asks if you also want to erase the corresponding audio file. This saves hard drive space used by bad takes and unwanted recordings.
Select the audio region, and press the Delete key.
This will remove only the audio region from the arrangement, not the audio file (from the Audio Bin). No dialog appears. This prevents you from accidentally deleting recordings that may be used in other projects. If you actually want to delete the corresponding audio file, you can do so by choosing Audio File > Delete File(s) in the Audio Bin. The deleted audio files remain in the Trash until emptied.