The term "MP3" has become something of a generic phrase for digital audio. However, MP3 files are just one type of digital audio, and there are many more out there.
All of them do the same thing: take music and save it as a computer file that's small enough to be downloaded quickly and stored on a portable player. In comparison, a CD track takes up around 11 times the space of a standard MP3 file, while sounding no better.
These digital audio files can be downloaded from an online store and then transferred to your player. Alternatively music tracks can be ‘ripped’ from audio CDs that you already own, to a laptop or desktop computer, using software such as Windows® Media Player or iTunes.
As mentioned, while MP3 remains the most popular format, a number of alternatives do exist. These include AAC for iPods, WMA from Microsoft and ATRAC from Sony.
When buying digital tracks online - such as from the Tesco Entertainment site - it's important to make sure your player is compatible. MP3s are universally supported, most players support the AAC format, and WMA is supported by most players except the iPod range. However software such as iTunes will convert WMA or MP3 to a suitable format for your player.
All these formats use something called ‘bitrate’ to control their audio quality - this refers to the amount of digital information used to store the audio.
The base standard is 128kbits per second, which roughly equals 1MB of storage per minute. The higher the bitrate the better the quality, but it's generally accepted that 128kbps is close to CD quality.
In the same way that MP3 has become the familiar term for digital audio, MP4 has become associated with video playback.
Technically, MP4 can be used to encode both audio and video but generally it's restricted to video, which is why many portable players that support video are called MP4 players.
As with MP3 audio files, video files need to be downloaded or ripped on your computer and transferred to your player. For iPod owners, iTunes offers downloadable films and TV shows ready to watch. For other players, however, you will need to convert your own videos to a suitable format using software such as Handbrake.