Any audio source that has been converted to a digital form. CD-quality audio is usually the standard that it refers to, that is, audio sampled at 16-bit resolution and 44.1 kHz sample rate. This standard refers to the Red Book standard in the audio industry.
Audio that has been encoded in a digital form for processing, storage, or transmission
Analog sound waves stored in a digital form; each digital audio file can be decomposed into a series of samples.