Could you explain these words: head ; side

Posted by Sphinx on October 16, 2003

1.Researchers found that classical music encouraged people to spend US$40 per meal. The bill comes to US$35 a head when there no music at all.
(a head?)

2.Kaka hopes to play a bigger role as captain of the under-23 side that will take part in 2004 Olympic Games.
(under-23 side? )