Richard,
A M is the way we used to comminicate via voice on the ham bands, 
likely long before you were born!  Not to begin a long, old fart rave 
about the mode, but it was the way that things were in the late 
fifties when I got licensed.  However, single sideband was coming 
along then and eventually A M lost favor.  The cons are that it takes 
up at least double the bandwidth of a voice comunication using both 
sidebands.  And, watt for watt it takes more power than an equivalent 
sideband transmission.  And a good A M transmitter requires a lot 
more engineering than its sideband equivalent.  I'll back away from 
that a bit and say different engineering and equipment.
The big pro is the possible great sound of A M.  If you listen around 
seventy-five and forty meters, probably more night time than day, 
with your receiver set to A M, you may hear some really good sounding 
transmisions.  There are a few hams still enjoying the mode a 
lot.  When ten is open, the frequencies just above 29 mhz. might have 
some A M transmissions around.  And it is a mix of old, fifties and 
earlier equipment and the newer transceivers that you will hear.
I could go on a lot longer but this should give you the 
idea.  Occasionally listen on ten meters and try the other lower 
frequency bands after dark and find out what there is to hear.
Hope this helps.
Pat, K9JAU who started on A M and still loves the memories.At 10:41 
AM 11/22/2014, you wrote:
>Hi!
>
>
>
>As a new ham, I am curious about the AM mode.  I would like to learn a bit
>more about it.  I think I basically understand the USB, LSB and FM modes,
>but the AM mode is a mystery to me.
>
>
>
>When, where and why does one use AM?  What are the pros/cons of it?  Can you
>direct me to some reading about its use?
>
>
>
>73,
>
>Richard KK6MRH