Email Addresses

This is probably a stupid question, but I haven't been able to find much info about it online.  Anyway, my email address is with Yahoo! and sometimes I will get an email from someone(they are using gmail) and it will just show the persons name for the address and other times it will show their email address only the first letter is capitalized.  Could this be two different people?   Why does it change from email to email?

email this address and ask them to hack your yahoo account.

satan666@hotmail.com

Are they in your contacts?

You don't read your headers first? Enjoy being phished and scammed, bor.