Ambika,
I believe you need to write the esse about the spam and asking the basic questions in a hope that gurus will do this job for you. I am sorry if I am wrong but based on how you wrote the questions, you need it not for yourself but for your professor.
There are many sources on the net that cover spamming and scamming, just Google it or go to Wikipedia.
If you really want to know more, perhaps take a look at my blog where I cover it in details introduciong my method to fight with it.
1)
Secure Cyber: * My War with the SPAM
2)
Secure Cyber: My war with a Spam. Continue...
3)
Secure Cyber: Update to SPAM text file has been posted