[Techtalk] newbie mail question

[alice]

I'm a little bit confused about my mail.

When I use the KDE Mail Client (KMail) I don't always get all my mail.
(but I do get some of it)
When I use the text based mail client pine, it all seems to be there.
Why is this?

I read somewhere that mail goes in /var/spool/mail/alice or some-place,
then you've got one program that fetches your mail from the server 
(fetchmail?)
and another program that sends your mail to the server (sendmail?)
and then you've got a mail client for viewing your mail and putting it in 
folders and stuff... like pine and KMail. i forget what these ones are 
called, MUA's ??

When pine or KMail shows me my mail, does it move it out of 
/var/spool/mail/alice 
and put it elsewhere, is it possible that pine is pinching the mail out of 
/var/spool/mail before KMail can get its hands on it?

Can anybody recommend me a good tutorial on the ins and outs and ups and downs 
and inside-outs of mail in the general and the specific?