rsync problem

[Matthew S-H]

I've been getting this problem:

~/ foo1$ rsync -vcart --progress foo2 at www.foo.com:~/ 
/home/foo1/Desktop/goraku/
Password:
bash: line 1: rsync: command not found
rsync: connection unexpectedly closed (0 bytes read so far)
rsync error: error in rsync protocol data stream (code 12) at 
/SourceCache/rsync/rsync-14/rsync/io.c(342)
~/ foo1$

Why won't it work?  And what does this error mean?  What can I do about 
it?

~Matt