If you've basically ever saved a sound file, you're most likely familliar with good 'ol MP3. It's a format that's been around for so long that it's patents have expired, and is ubiquitous in the realm of online music sharing. 128Kbps is generally seen as the baseline for acceptable audio quality for casual listeners, with high bitrates (up to 320Kbps) generally only being used by people who take audio quality at least somewhat seriously. FLAC is usually the format of choice for audiophiles for it's lossless nature and capability of being used with Hi-Res audio (usually referring to audio with a much higher sampling rate and bit depth than an audio CD).
