Questions about maize varieties

[jasmine]

Dear sir,
I'm Pu in Thailand. I'm studying now and my teacher gave me to find 
the varieties of maize. But I don't know how many varieties of maize 
and also corn (are they the same?)  I found dent corn, flint corn, 
sweet or popcorn but some book they were classified into hybrid. 
Which is correct?  So could you recommend the web site or book which 
have these varieties of maize or corn and how to classify them in 
each item. My e-mail address is pupeait at yahoo.com
Thank you in advance for your help.
Pu