Shell selection

[MIKE PATTERSON]

I have a few novice questions concerning unix shells.
I know that a variety exists: C-shell, Bourne shell, Korn 
shell.  However, I'm not aware of _why_ there are several
shells as opposed to one.  Please try to address the 
following:

  1) Are there shells other than those mentioned above?  
  2) Is any one shell more popular among users than the others?
  3) Is any one shell more popular among installations than
     the others, and why?

The reason for asking is that I don't care to learn about
all of the shells - I'd rather devote my time to the one
shell most likely to suit my changing needs over a period 
of years.  The machine now at my disposal has the three
shells mentioned above.  Since each seems to be equally 
cryptic, I'd like to stay with just one. 

I realize that these are questions subject to opinions so 
please respond with whatever facts you know.  E-mail is
fine for responses. 

Thanks in advance,

MIKE PATTERSON
Georgia Institute of Technology, Atlanta Georgia, 30332
uucp:	  ...!{decvax,hplabs,ncar,purdue,rutgers}!gatech!prism!ae221mp
Internet: ae221mp at prism.gatech.edu
-- 
MIKE PATTERSON
Georgia Institute of Technology, Atlanta Georgia, 30332
uucp:	  ...!{decvax,hplabs,ncar,purdue,rutgers}!gatech!prism!ae221mp
Internet: ae221mp at prism.gatech.edu