Vorbis is an "open-source" digital audio compression format — that is, it exists in the public domain and is completely free for commercial or non-commercial use. Because Vorbis is most often used in conjunction with a digital A/V container format known as "Ogg," it's usually referred to as "Ogg Vorbis." Vorbis, like MP3, is a "lossy" compression system, removing frequencies deemed inaudible. Both formats offer variable-bitrate encoding options (MyRipper does not support MP3 VBR), for better efficiency. But the algorithms Vorbis uses to decide which information to discard differ from those used by MP3. Proponents claim that the Vorbis format outperforms MP3, producing files that are significantly smaller than MP3s of similar sound quality (or files that sound better than similarly sized MP3s).