What started with the Sony Walkman has grown into a bonanza of compact MP3 players. These small devices can store and play music files, but most models can now also play video - giving you a complete mobile entertainment experience. All you have to do is choose the one you want.

MP3 players fall into two distinct categories:

MP3 players offer a variety of features that range from displaying your digital photos to playing interactive games. Some, like the iPod Touch, can even wirelessly access the internet and download further applications. These are some of the extras to look out for:

Battery life: this varies a lot. Small flash memory players without LCD screens tend to last the longest. The actual figure in hours will be quoted by the manufacturer.

Capacity: the amount of memory dictates how many songs you can fit onto a device, and this figure is always prominently marked on the packaging in MB (megabytes) or GB (gigabytes).

Resolution: if you want a device that can also show digital images or video then screen quality is important. This is given as the number of pixels along the horizontal side, times the number along the vertical, for example 480 x 320 - great quality.

Software: MP3 players include computer software, so you can organise and load music onto the player. A programme called iTunes is bundled with iPods, and it works with both Mac and PCs. Other software might only be compatible with PCs. 

You will need to connect your MP3 player to a computer in order to move MP3 files, or other files onto it, but you might not need to buy additional software. MP3 players, including iPods, can connect to a PC or Mac via a USB cable. If your computer has a CD drive it’s simply a case of dragging compatible music files onto the device (as it appears on the computer’s desktop) to play them.

Alternatively, a programme like Apple iTunes lets you move and organise your music on your Mac or PC, before transferring to your iPod. Most other MP3 players come with their own applications for organising music on your computer. Check it is compatible with your computer, as some will only run on Windows operating systems.

There are many different formats, or types of music file, around, but MP3 is the most common. Although they are called 'MP3 players', most devices can read all other formats too, so you won’t usually have to check compatibility. To be sure, check the product features for compatibility with the main formats like WMA (Windows Media Audio) and AAC (Advanced Audio Coding), favoured by Apple, and AIFF or WAV formats - the uncompressed music files you find on a regular CD.

Headphones: basic versions are usually supplied with a new MP3 player, but you can improve on sound and comfort by buying better quality ones. Over-the-ear phones usually offer superior quality.

Case: protect your MP3 player in a plastic, rubber or leather case. The more popular the model, the more options you will have - so for iPods, you’ll be spoilt for choice.

Docks: usually mains powered, these provide a cradle for your player and speakers to amplify its sound. There are many types to choose from, with a cradle that will also recharge your MP3 player.

Speakers: turn your MP3 player into a portable hi-fi by adding separate loudspeakers. Powered speakers with their own batteries plug into the headphone socket of your player and boost the sound to fill a room. Large desktop speakers can give you an even louder performance.