MP3 files are the latest music craze. You can now download millions of songs to your computer, or to your portable MP3 player, and you can even transfer ("burn") them to CDs. People all over the world can connect to the Internet and share music -- you never know when you'll stumble across an unknown Swedish band that you absolutely love, and you'll have MP3 technology to thank.

In this edition of HowStuffWorks Express, we'll learn what MP3s are, how they work and what "burning a CD" really means.

How does music get into your computer? The music must be digitized (converted into a series of 1s and 0s) to be stored in your computer. An MP3 file takes it one step further. Every music file on a CD is made up of units of data called bytes. An MP3 is special because it compresses the file -- it shrinks the number of bytes so the file takes less time to download (read on for an in-depth description of how this works).

When you listen to an MP3, your computer uses software to expand the compressed file to its original size. Then it sends this file to your sound card. The sound card turns the data into an analog wave for the speakers so you can hear the music. Incredibly, MP3s sound almost as good as CDs, even though they take up about one-tenth of the space that uncompressed files require. This may seem very strange. How can the expanded file be identical to the original file before it was compressed, and where do all of the extra bytes go? The basic concept is surprisingly simple.