ln creates links ( which come in two flavors - hard and soft. see "man ln" for details) ln -s creates a soft link between two items. if you execute the following in a console, perhaps it will be more clear:
Code:
ls -l /lib | grep libc
NOTE: the following is from my system, yours may differ
ls -l /lib/ | grep libc
-rwxr-xr-x 1 root root 1357414 2005-01-29 01:01 libc-2.3.4.so*
lrwxrwxrwx 1 root root 13 2005-03-26 03:09 libc.so.6 -> libc-2.3.4.so*
-rwxr-xr-x 1 root root 191040 2005-01-29 01:01 libcidn-2.3.4.so*
lrwxrwxrwx 1 root root 16 2005-03-26 03:10 libcidn.so.1 -> libcidn-2.3.4.so*
lrwxrwxrwx 1 root root 17 2005-03-26 03:06 libcom_err.so.2 -> libcom_err.so.2.1*
-rwxr-xr-x 1 root root 6264 2004-04-12 01:40 libcom_err.so.2.1*
-rwxr-xr-x 1 root root 25168 2005-01-29 01:01 libcrypt-2.3.4.so*
lrwxrwxrwx 1 root root 17 2005-03-26 03:09 libcrypt.so.1 -> libcrypt-2.3.4.so*
the ones with -> are soft links, all they do is point to something. so take libc.so.6, it points back to libc-2.3.4.so - note that there is no "actual" libc.so.6 on my system, just a link named libc.so.6 ( which, if any program request libc.so.6, the program will find the libc.so.6 which points directly to libc-2.3.4.so ( which is what the program will use)).
as far as adding your icon, this depends on what you are running (kde, gnome, other?) generally, all you have to fill in is the name, command ( in this case the command is just mozilla), and (optionally) choose the icon you want associated with it. for a desktop launcher, you will want the 50 size icon. for a menu, choose the smaller one (mozicon16.xpm)