When we communicate with our subconscious mind and our conscious mind is aware about it, it is hypnosis
When we communicate with our subconscious mind and we do so without being perceived by any of our 5 senses, it is called subliminal. Examples are advertisers flashing words in rapid succession such that you do not really see it with your eyes but are totally taken in by your subconscious mind.
The same applies to audio messages. The words are embedded in the music. You hear the music but not the words.
Both hypnosis and subliminal are aimed at influencing your subconscious mind.