I gave this explanation to my wife last night on SMTP, so hopefully it will help...
SMTP stands for Simple Mail Transfer Protocol... you can think of it as a
mailbox. When you need to send mail to someone you put the mail in the
mailbox, and a mail person comes and picks up the mail and sends it to where
ever it needs to go.
Now pretend that we didn't have Canada Post to send our mail and in order to
have your mail sent you had to subscribe to a mail service, so that you had
access to their mail box, so that their mail person would come pick up the
mail and deliver it for you.
I subscribe to Shaw cable, so they offer me their "mailbox" or SMTP server
for me to send all my outgoing mail through... If I want to send mail through
GMail's SMTP server I would need to have access to it.
HTML Forms...
There are many types of HTTP commands that are sent to a server the 2 most
popular are GET, POST.
The GET verb requests a resource from the server, like a web page.
The POST verb sends data to the server like in a contact form.