You will need an MP3 player and possibly an Ogg Vorbis plugin to
listen to the recordings. Ogg Vorbis plugins are available for
most MP3 players. The table below lists some MP3 players that can also
play Ogg Vorbis files.
The web sites for the MP3 players have instructions for getting hold of the Ogg Vorbis plugins if one is required.
Because the name is so weird! Seriously, the principal reason is that MP3 is patented technology and royalties are due for using it.
If you compress your own audio using MP3 and have not paid royalties due on the encoder, you are committing a crime. This is the case even if you use an open-source or shareware MP3 encoder.
By using the Ogg Vorbis encoder nasty patent legalities are avoided. Besides, many consider that the Ogg Vorbis coder gives higher quality results. See the Ogg Vorbis FAQ for more discussion of the issues involved.