what are zombies

[David Hamm]

I had a strange thing happen Saturday.  I tried to get in to my Linux =
box from home using ppp and it wouldn't answer, which in itself is =
unusual, once I got to the console I did a ps -x and noticed that =
several of the daemons were marked as  zombie.  I looked through the man =
pages and found nothing that clearly described what zombies are. Then I =
tried to kill -9 them but they would not unload from memory.  Any =
information would be helpful.

Thanks

David