MP3 is short for "Motion Picture Experts Group 1, Layer 3." An MP3 is nothing more than a file format, much like ".doc," ".pdf" or ".jpg," that compresses files - specifically music files - without sacrificing quality in any noticeable way. For those new to the digital music world, the MP3 and MP4 formats are compression technologies for converting standard analog audio tracks, like those on a commercial music CD to smaller digital computer files.

The main reason digital music formats have become so popular is that they deliver high quality sound at roughly one tenth the size of the uncompressed original. As a point of reference, a standard Audio CD can hold roughly 18 to 20 songs while a CD encoded with MP3 files can hold up to 250 songs, depending on size.

Today, iTunes, Apple's music/movie player and media management software and online store is a success that is driven by the MP3 and MP4 technologies. Apple was the first commercially successful attempt at selling music at 99 cents per song but required an iPod device if you wanted to take your purchased music mobile.Unlike other companies, Apple has been convincing the music industry to allow it to sell copyrighted music in a digital format because of something known as FairPlay digital rights management (DRM). Remembering that this all came on the tails of the massive music piracy problem created by the original Napster file sharing system (Napster is now a legitimate online music company), Apple had to demonstrate that it could control how these digital files were used.

No doubt about it, iPod is the most successful portable entertainmnet device today, but other devices such as RIO, DELL and iRiver are also very successful, easy to use and affordable.

This is where the AAC format (Advanced Audio Coding, commonly referred to as MP4) came into the picture. Because Apple used a proprietary file format, it was able to limit how each file purchased on its system was used, which meant a single user could not purchase a song and share it with others.

MPEG-4 is the global multimedia standard, delivering professional-quality audio and video streams over a wide range of bandwidths, from cell phone to broadband and beyond.

MPEG-4 was defined by the Moving Picture Experts Group (MPEG), the working group within the International Organization for Standardization (ISO) that specified the widely adopted, Emmy Award-winning standards known as MPEG-1 and MPEG-2. Hundreds of researchers around the world contributed to MPEG-4, which was finalized in 1998 and became an international standard in 2000 and included in QuickTime in 2002.