If you look at the descriptions and specifications of the music phones and all you see is a load of incomprehensible numbers and letters, don't worry, you're not alone! That's why we've compiled this glossary - to tell you all you need to know in everyday language.

File types

The first area to look at is file types which can be played on your mobile. To be played on a computer, iPod, MP3 player or mobile phone, music must be converted into a digital file (a series of 1s and 0s), and there are several types of file (or formats) to choose from, generally known by, you guessed, numbers and letters.

MP3

The most popular format is MP3 - it was developed by an industry body called Motion Picture Experts Group (MPEG) and it was audio layer 3. It works by removing from the track parts of the sound (frequencies) which are inaudible to humans, leaving a much smaller amount of information so the file size is smaller, and you can fit more tracks into your memory space. Quality-wise it's not as good as CD (although you can get different bit rates of MP3 giving different qualities) but most people don't hear the difference and are happy to listen to MP3 files all the time. MP3 files don't currently support DRM (digital rights management, software protecting music sold from being copied) so most of the music download stores don't use it. However, now that record labels are starting to offer music without DRM for a higher cost it's possible that MP3 will make it into the stores again.

AAC

AAC (Advanced Audio Coding), also known as MP4, is a newer format which compresses the sound much like MP3 does but does it more efficiently, meaning you can have higher quality in a smaller file. It's the format used by the Apple iTunes store and does support DRM (see above), and an AAC filename will usually end with .aac, .m4a, .m4p or .mp4. You may also see AAC+, or High Efficiency AAC, which is just a development of, and improvement on, the original system.

WMA

WMA (Windows Media Audio) was developed by Microsoft, and is also similar to MP3 but can produce high quality audio at about half the bit rate so the file can be about half the size. WMA also supports DRM for copyright protection of the music stored.

WAV

WAV is the standard format of full-on, non-compressed music for Windows, giving CD quality but needing a large file size (about 10Mb for a song) so is not practical for use in mobiles etc.

AIFF

As above but the standard format of full-on, non-compressed music for Apple Macs. It stands for Audio Interchange File Format, in case you're interested...

Memory and storage

File sizes for music, photos and videos on your mobile are measured in Megabytes or MB, which is roughly a million bytes of information. One MB is equivalent to about one minute of good quality MP3 audio, so your average song in the music player will take take up 3-4 MB of memory. Most mobiles have only a small amount of internal memory (normally up to about 80MB, although the Sony Ericsson W950i has an amazing 4GB) so you need to add extra memory in the form of a memory card if you want to store a lot of songs. Memory cards come in the following sizes; 128MB (about 32 songs), 256MB (about 64), 512MB (about 128), 1GB (about 256 songs), 2GB (about 512) and 4GB (about 1024 songs). GB stands for gigabyte, which is around a thousand million bytes of information. Memory cards also come in different formats, mainly Sandisk Micro SD, Sony Memory Stick Pro Duo and Sandisk Mini SD.

Sandisk Micro SD

A miniature version of the original SD (secure digital) memory card, the Micro SD is the smallest type of card currently available. It is also known as Transflash memory and is supported by phones such as the Nokia N95 and E65, the Prada and Shine phones by LG and the Samsung U600 and D840.

Sandisk Mini SD

Physically larger than the Micro SD, used in the Nokia 6300 and N73 among others.

Sony Memory Stick Pro Duo

Sony Ericsson music phones use this format, a miniature version of the original Sony Memory Stick.

Bit Rate

Bit Rate, referred to in the descriptions of different file formats, is simply how much data is transferred or encoded in one second. It's measured in Kbps or KiloBytes Per Second, or thousand bytes of information every second, and affects the size of the file considerably. For example, WMA files are reckoned to be able to produce near-CD quality at 64 kbps, whereas MP3 has to be done at 128 kbps to sound that good, so the WMA system can get the same quality with half the file size - a big advantage. 192 kbps is about the highest rate you ever need to use, as the human ear would have trouble teling the difference between that and a higher quality.