Human: What is the difference between a cd and a mp3? Assistant: 
The main difference between a CD and an MP3 file is that CDs are made up of multiple layers of different types of materials, such as plastic, aluminum, and dye, while MP3 files are typically compressed digital audio files. CDs also have higher storage capacity than MP3s, which can be beneficial for music collectors or audiophiles. Additionally, CDs can be played in most CD players, whereas MP3s require specialized software to be able to play them back.