is aac lossy or lossless?
Lossless includes formats (or codecs, short for coder-decoder algorithms) such as Apple Lossless and FLAC (the Free Lossless Audio Codec). Lossy includes the ubiquitous MP3 and AAC formats. (AAC, which stands for Advanced Audio Coding, is, in reality, the MP4 format, the successor to the older MP3.