MP3 players are small gadgets dedicated to storing and playing digital media files, especially music files in MP3 format. There's a certain amount of functional crossover with tablets and smartphones, both of which can also download, store, and play music files. However, MP3 players have the advantage of being smaller and cheaper than either tablets or smartphones. An MP3 player typically tucks into a pocket, where it rides unnoticed except for the cords connecting it to a set of headphones or earbuds.
MP3 players are available from Apple, Sony, Samsung, and other computer and electronic manufacturers. In size, they range from the Sony NWZ-270 Walkman Sports, which is essentially a pair of headphones with an MP3 player built in, and the Apple iPod Shuffle, which is coin-sized, to devices the size of a smartphone. There is still some trade-off in size for sound quality.