To create a new email, you have several options.
New creates new email. This will have as a category and subcategory the default.
New and Sent To creates new email, along with the SendTo from the address. The category and subcategory will be the default.
Reply creates new email, with the body and SendTo fields the same as the previous. If Reply All is pressed, the reply email will be to all the people in the first list. If Reply One is selected, it will be to that one person.
New Fax creates new email, with the SentTo as a fax, i.e., the CC field is "x".
The next two menu items create a new email record which is something filled out on the Internet, such as a letter to a politician. The last item adds a record of something sent as a letter.