ALAC stands for "Apple Lossless Audio Codec" and is a lossless audio compression format developed by Apple. It enables audio files to be compressed without losing any information, resulting in sound quality that is true to the original. ALAC is widely supported by Apple devices and platforms such as iTunes and iOS, allowing users to store and play high-quality music files with less storage requirements. It is a popular choice for audiophiles and music lovers who prefer high sound quality.